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1. ID to switch off the heater with ID to switch the pump to a certain operating voltage 0 off 256 full speed e STAT to get the current status packet 40 e STPR 2 bytes to set the threshold pressure for start and stop of the census phase for automatic mode is written to EEPROM preset to a value TBD before launch e STTI 2 bytes to set the number of seconds from launch onwards until the start of the census phase for automatic mode is written to EEPROM preset to a value TBD before launch e AUTO to switch the microcontroller manually to Autonomous Mode e GETP 2 bytes ID to get the packet data or status with ID that was previously saved in memory e DATP to get a current data packet The possible responses from the balloon are e a data packet responding to the command GETP DATP e a status packet responding to the command STAT e command OK responding in all other cases 3 7 6 Handshaking Data packets serve as a heart beat signal from the experiment as they are transmitted every 10 s and signal a healthy downlink The ground station responds with OK Since it is not possible to determine from the whether the uplink is working the ground station will once every minute send a HELO command waiting for a HELOOK 3 77 EEPROM The EEPROM can accommodate 4
2. Mechanical interfaces be 8 Rau EE aW 3 2 1 Accommodation Requirements 3 2 2 Attachment Concept and Foot Pattern Thermal interfaces ss G x sl G tt 3 3 1 Thermal Design r aa KENT der 3 3 1 1 Thermal Design Requirements 3 3 1 2 Thermal Design Description 3 3 2 Thermal Interfaces_ es ERE E a sa a 3 3 3 Temperatures and Thermal Control Budget 3 3 3 1 Temperature Ranges 5 230399 3 3 3 2 Temperature Monitoring Power interface requirements 3 4 1 General Interface Description 3 4 2 Power Distribution Block Diagram and Redundancy 3 4 3 Experiment Power Requirements 3 4 4 Interface Circuits er 2 etta te Pea Connector and Harness Requirements 3 5 1 Interconnection Harness Block diagram 3 5 2 Interconnection Harness Characteristics 3 5 3 Connector Types sev ELE Sake ae 3 5 4 Connector Pin Allocation GR OBDH Interface Requirements 3 6 1 E Link connection 3 6 2 Channel Allocation NG 3 6 3 Bit Rate Requirements Se KEE AE ite 3 6 5 Monitoring x eg SA ees 3 6 6 Electrical Interface Circuits 3 7 Experiment Software and Autonomous Functions 3 7 1 Software Flow Diagram and Functional Requirements 3 7 2 Design for Redundancy amp Shutdown
3. 3 7 3 Pump Instrument Operating Modes 3 7 4 Packet Definitions gt ar die e ee ee X Y 3 7 5 Telecommand Definitions as va aa o omoes 300 Handshaking ci s scat emu b NAS LAE Ey ons IEPRONL I LIS eM IO ESS 3 8 Electromagnetic Compatibility Requirements 3 8 1 General EMC Requirements 3 8 2 Specific EMC Requirements Grounding sis Gh WR See oe DRE Ge Seid 3 9 Cleanliness Design and Contamination Control Requirements od MiItigabion SE scar ce ane GE hod MG SS 2 9 Lil Recovery vx ws we SE a EK E Verification and testing 4 1 Experiment verification plan denses de 41 1 Objectives a 4 1 2 Responsibilities e NG 41 3 Verification by Analysis sert 16 396 3 Gh 4 1 4 Verification by Test EEN 41 5 Verification Control System 4 2 Experiment e d KEEN 4 2 1 Microcontroller Testing m ra Redes 4 2 2 Microcontroller Qualification Requirements 4 223 Electronics Testing ole 4 RECEN oe dk AG 4 2 3 1 Control Box x 58 b nd Ge fet 4 2 3 1 1 Results of control box thermal test 4 2 3 1 2 Results of control box vacuum test 1700040 4 2 3 2 1 Results of battery thermal test 424 Pump Testing sudeste ME Rae Ms GE dues 4 2 4 1 Vacuum Test call nA x st ba ee x 174111 Test Procedure 232 kee a 4 2 4 1 2 Acceptance Criteria 4 2 4 2 Thermal est EE 4 2 4 2 1 Test Procedure 4 2 4 2 2 Acceptance
4. surd 089 WoO EMO SIAMO 429 429 1 2 0 08 8260 60 V N Joputg yoos surd 2 089 uoO semi Z AH 96 6 96 I T0 08 C160 60 V N Joputg 194208 surd y 089 UOD IeM GI OT 90 Z 90 00 TZ 0 60 V N Jopurg Sn d surd 9 089 uoO IRINIIO D Z AH P 96 8 Str 4 60 00 4080 60 V N Joputg Su d surd 089 IMNO 10329UuUO0 GI T 82 0 Y reoepors sa 0996288 Ao3srurieu SIAMO Og Lb OS Ly I UPTVSTOXASV 9892617 TOUTE JOSUDG 9ANSSIIJ SIOSU9S snj3ejg una 303 3509 s rdi 3509 440 JoquinN 32npoiq ioquimw SuriopiQ Jon ddng quauo duo 79 Power W Table 8 Power Budget Pump 10 2 Control Unit 5 Heater 5 Actuator 11 total 31 2 Items Mass g Frame 1 952 20 Pump 815 30 Control box 730 00 Battery box 609 90 Actuators 1 709 00 Batteries 876 00 Connectors 88 00 Tubing 680 00 Valves 140 00 total 7 600 40 Table 9 The mass budget for the Stratospheric Census Experiment A conservative estimate for the total mass is 8 kg allowing for some additions 80 F Gantt chart 81 8007424010 sisA euy 1u uulu dx3 suolejay IYUS peunsse 35Nvus3 01 APA 6unsal TD Sunset Buns r Ajquiassy Aquassy y gt uag Wooiuea Butuea 1uauoduo
5. 2 3 3 5 Flow Analysis Saco eode mes 17 2 3 3 6 Vibration Analysis lt See ee Le OS 18 2094 AMPU pS ln E dia re 18 2341 Pump ivpesnco ed aeu Xi EN 18 2 3 5 Filter and Sensor Subsystem Payload 19 2 3 5 1 Filter requirements 2523994 desk 19 2 3 5 2 Choice of filter Ea SENS a 20 EE 22 2 4 1 Computer Systems amp Data Storage 22 2 4 0 Qualitative Software Requirements 22 25 Normal Mode su d isa sae Hore EE 23 244 Autonomous Mode 494 e atk her a eh arada d a 23 2 1 Further Details a ee Dean S 24 257 UPON se nA tes IR d t x e es de AG A 24 2 5 1 Measured and calculated flight information 24 2 5 2 Location in the gondola silba AE ket 24 253 Preflight procedures lc bao 4 br d ERR 25 25 4 Post flight Analysis D vr ox Q o z bb eG 3 Experiment Interfaces and Design Requirements 3 1 3 2 3 3 3 4 3 5 3 6 General Design Requirements 3 1 1 Fault Tolerance Design uc vade 4 e aol Electronics saa r Eee a Ee ae ede s 3 1 1 2 Microcontroller Safety amp Risk of Failure JETS Strutture e uoce E eo Ke ET 3 1 1 3 1 Single point failures 3 1 2 Safety CONCEP o cun sv S ee m bib Beles Materials a s xot k Saa su S A a us wh S S s Cb res lu G cae ede code s us s Dog Brass Y s lu ke s ste NQ E n Uto d bd HCl ig scere Ape bey emu kr opis 3 1 4 Declared Components List
6. L Stratospheric Census Ground Station Temperature Packet Log Control Box 10 Pump 20 Update Data Pressure Timestamp 2 Amber 10 Counter 4923 ER TAKS x Valves ee zeen EE Update Status Pump Heater Experiment Commands Set Pump Voltage Set 2 Way Valve Set Switching Valve Heater OnJOff Autonomous Mode Mode Requirements Uplink Downlink Uprklast ELO bandshake RE bomirk pada RRE Command Execution GC HELO Vr Figure 14 Ground station user interface 5 1 5 Compliance No further action necessary for the electrical equipment as these are stan dard components In general the working conditions for the ground station are uncritical and the same during development and flight only satisfactory operation during all other test runs is necessary for compliance 5 2 Ground Operation Requirements If the experiment is in Autonomous Mode no interaction from the ground is necessary If the experiment is in Normal Mode the ground operator is mainly responsible for the control of the pump and the valves and the supervision of all data values temperature and pressure The following tables gives a summary of all ground operation requirements 56 pueuuos pues pajedpnue unile yurda pow SNOUIOUOJNE OF u23IMS A enueuu sAndadsal ayy pues suonduunsse wo suonipuoo 461
7. RE EuroL auncH BEXUS Student Experiment Documentation SED PROGRESSUM Document ID RXBX 08 03 10 SED vers41 doc Mission BEXUS 7 Team Name STRATOSPHERIC CENSUS Team all Lule Tekniska Universitet Sweden Student team leader Martin RUDOLPH Team members Gerrit HOLL Mark FITTOCK Martin SIEGL Jaroslav URBAR Experiment Title Stratospheric Census Version Issue Date Document Type Valid from S 22 September 2008 MTR 22 September 2008 Issued by Experiment Scientist LULE TEKNISKA UNIVERSITET Approved by K Swedish Space Payload Manager Corporation n EX chip45 SESA amp ELmarco Change Record Version Date Changed chapters 2008 02 29 New Version Blank Book 2008 03 10 Marked Changes Student distribution 2008 04 14 All PDR 2008 05 08 All PDR for IRV 2008 05 26 All CDR for IRV 2008 06 02 Minor Corrections CDR for ESA DLR Eurolaunch 2008 09 22 Current Status Test MTR Launch campaign Final report Abstract The Earth stratosphere contains aerosols of various origins An experiment is proposed to fly a filter on a stratospheric balloon catch stratospheric dust aerosols on this filter and perform an analysis of this dust on ground Keywords Stratospheric dust aerosols BEXUS 7 stratospheric balloon aerosols Abstract The Earth s stratosphere contains aerosols of various origins including aerosols of volcanic and cosmic origin An experimen
8. B e The gondola G e Other experiments O e The own experiment E 43 For each of those the amount of contamination for the experiment can be approximated as the product of the outgassed mass times the fraction of outgassed mass that impacts the surface Source amount g hour fraction impact g hour Balloon 102 1075 107 Gondola 1071 1074 10 Others 1077 107 1077 Us 1073 1 1077 Total 102 251075 21077 Table 3 Estimates for outgassing amounts Note that those are extremely rough estimates and that the estimated values can be off by three orders of magnitude or even more m table 3 are estimates for the outgassed mass The figures in this table are highly unreliable and need to be updated as more information becomes available We estimate to receive around 0 1 gram of stratospheric dust and 2 milligramme contamination per hour This would be an acceptable contamination level as it would in total be around 1 of the mass of the captured aerosols which would in turn be around 0 1 of the mass of the filter all very rough estimates 3 9 1 Mitigation Even without knowing how much contamination we can expect we can list a number of techniques to use to prevent contamination as much as possible Contamination from the balloon is expected to be worst during launch and during descent Our experiment has a front valve preventing any par ticles from entering the hose during launch
9. Esrange is located in the municipality of Kiruna Norrbotten county in Swedish Lappland at 67 53 38 67 8938 N 21 6 25 21 10694 E at an altitude of approximately 300m This region has a subarctic climate DfC in the K ppen classification system In the heart of winter ground temper ature is usually around 15 C but temperatures as low as 48 C have been recorded Precipitation is relatively low all year round D 3 2 Balloon Trajectory Winds at an altitude of 30km are generally westerly between September and April and its velocity is maximal around January February The maximum wind velocity that has been observed is 38022 at 10 February 1974 The winds start slowing down early March and turn around by the end of April During this time the wind direction is unstable The flight time during January February might be as low as 1 2 hours 4 In April and September 74 flight times of 5 10 hours are likely Much longer flights are possible but for political reasons the balloon will descend before flying into Russia The balloon will land somewhere in northern Sweden The temperature in the stratosphere at 30km is about 60 C 1 75 N r NUMBER cm 1072 10 10 10 RADIUS jem FIG 3 Integral particle concentration versus particle radius measured by photoelectric particle counter for the 1971 74 period The data are approximated by log normal N expo nential Na and restricted power l
10. successfully controls the experiment while it is in the space simulator 5 successfully controls the heater under varying fluctuating temperature conditions The test of Autonomous Mode 3 should be part of a full worst case test including e simulated loss of communication several times during ascent and dur ing floating e fast temperature fluctuations simulated by stimuli or real in the 50 to 50 range e loss of power during ascent floating and in Autonomous Mode A report shall be given for each of the prescribed tests It shall contain the final test parameters and the test result In case of non compliance 4 2 3 Electronics Testing 4 2 3 1 Control Box All electronic components are commercial with dif ferent industrial standards Temperature ranges are stated in appendix E However all critical components are inside the heated control chamber which should always be kept between 0C and 85C to make use of the internal cali bration of the pressure sensor in this range 4 2 3 1 1 Results of control box thermal test The electronic box has been tested thermally using a thermal chamber The temperature was raised from room temperature up to 50 C The temperature sensors were calibrated using this thermal chamber No flaws were detected during this 4 2 3 1 2 Results of control box vacuum test The electronic box was placed in the vacuum chamber without any connection to outside The pressure in the v
11. 2 57 Actuator 18 10 1 8 0 25 0 45 Pump 11 10 1 1 5 5 9 Table 1 Experiment power requirements The figures marked with an aster isk are based on estimation Verification for those is required 3 4 4 Interface Circuits The main PCB will be connected to the E link provided by Esrange via a shielded twisted three wired cable On the E link site it will be connected via a MIL C 26482 series I connector The control box provides a circular socket for this interface see section 3 5 The MIL STD connector will be borrowed from Esrange for the time of flight 3 5 Connector and Harness Requirements 3 5 1 Interconnection Harness Block diagram Figure 11 shows the external interfaces provided by the control box The circles indicate the individual sockets and are denoted with acronyms having 34 Figure 11 Connector diagram See text for an explanation the following meaning POW Power line in ACT Actuator and pump interface RS232 Serial connection TEMP TEMP Interface to three external temperature sensors two op tional 3 5 2 Interconnection Harness Characteristics All interconnections are foil shielded with the shield grounded to the control box 3 5 8 Connector Types For all connectors the 680 series manufactures by Binder is used 2 All sockets are female to protect the circuit from accidental outside shortening Thus all connectors including the power connector are male Later does not cause an
12. 4 shows the CAD design from various angles 15 Figure 4 Structural design of the experiment 2 3 3 2 Manufacturing techniques Mark Fittock has been directly in volved in the construction of numerous engineering projects in the past However this has not included prior experience with construction of pipe and pump systems The other students involved in the project have more limited experience 2 3 3 3 Volume budget Originally Stratospheric Census requested a volume of 200 200 300mm However this was a very rough estimate and now that the problem has been extensively explored a volume of 300 350 200mm will be required 16 The length of 350mm has been estimated using the total length for cor rect orientation and taking into account the threads of the components required for the primary intake line The height requirement of 300mm is dictated by the actuators Valve B and the elbow used It would be possible to reorient this system and this may result in a smaller height The 200mm width is to allow space not only for the pipe and pump subsystem which requires approximately 100mm but also the control and battery array This has been given considerable space so that the batteries can be securely attached and to minimise risk of damage to the PCB 2 3 3 4 Frame Stress Analysis For the frame some stress analysis was conducted Firstly the failure mode needed to be ascertained Using worst case assumptio
13. 4 Timing No requirement on timing information for the experiment on the balloon A real time counter counting the seconds since power on will provide a timestamp for the packets On the ground this can be matched to real clock time 3 6 5 Monitoring Stratospheric Census monitors the temperature on the pump and in the con trol box housing the electronics For experimental purposes the pressure is measured as well Based on the temperature values either the microcon troller in Autonomous Mode or the ground station in Normal Mode 36 takes the necessary actions Commands are verified by the microcontroller based on a CRC checksum their execution acknowledged either by an OK packet and or a status packet 3 6 6 Electrical Interface Circuits Except for the RS 232 connection there are no electrical interfaces outside the experiment Since RS 232 uses a GND line the whole experiment has to be grounded to the E Gon gondola to share a common ground with the E Link unit 3 7 Experiment Software and Autonomous Functions 3 7 1 Software Flow Diagram and Functional Requirements The software flow diagram for the microcontroller next page shows the complete code structure including the switching of modes and the interrupt handling Transmission to the ground and data saving to the EEPROM is indicated as well 37 o e1 Be 4 ony 199 0 p Dei ed 185 yooro euin jeay 1ueuieJou HEIS 1dnueju
14. Criteria 4 2 4 3 Thermal Vacuum Test 4 2 5 Structural Testing yas rater rea 4 2 6 Full functional test results 4 3 Electrical Functional Performance Test 4 4 Limited Life Time Elements Ground station 5 1 Ground Control amp Electrical Ground Support Equipment Dd Concept sss a Sx rt A ele ew Bak fend e 5 1 2 Hardware Description Ages xbr 5 1 3 Network Interface asta S R s OR 5 1 4 Software Description amp User Interface Compliance no ft beet ene bar ske nk BOX Reno 5 2 Ground Operation Requirements Project Management 6 1 Organisation and responsibilities 6 2 Relation with various organisations 6 3 Schedule and Milestones 6 3 1 Planning of Phase D use n 3006039 6 3 2 Important Dates Sup ea a das 6 3 3 Mission Phases x into ar due sing EXE EUR o R RE 6 3 4 Current Shays e d ele Fama s OK ve 6 3 4 1 Mechanical Engineering 6 3 4 2 Software Engineering 6 3 4 3 Blecbroni s see goce ser ete ae doe Fa 6 3 4 4 Pump amp Filter ea TR d m st be 64 Configuration Control vag Bereet b y Bi DS 6 5 Deliverables 42 amare e a nt Electronics A 1 Circuit diagram eov ato ose xe a ka su SEP oou edi den A 2 Grounding diagram SEKT SSS SG A 3 Pin allocation E II pli
15. and ascent up to stratospheric altitude This valve is as close to the front as possible so that as few par ticles as possible can stick to a surface between the valve and the ambient atmosphere This valve will close again before descent so that contamination during descent and impact is as low as possible The distance between the pump with the filter in front and the ambient air is as small as possible so that the surface area of the hose which will outgas particles is minimised The preferred viewing direction for the experiment is straight down It is expected that this will be the optimal direction to prevent contamination particularly from the balloon 44 3 9 1 1 Recovery The experiment needs to be treated with care upon recovery in order to minimise the chance that the filter gets polluted 45 4 Verification and testing 4 1 Experiment verification plan Verification of the experiment is an important part of the project All designs are made such that verification and testing is possible and a significant amount of time is reserved for this in the time plan 4 1 1 Objectives The objective of the verification is to make sure that all subsystems as well as the whole system comply with the specifications requirements as well as the boundary conditions as defined by Eurolaunch 4 1 2 Responsibilities Each person is responsible for the verification of the part that he has designed and the whole group carries col
16. and downlink are working listen to commands from the ground station acknowledge commands from the ground station by sending an OK packet status packet control the heating elements automatically 2 4 4 Autonomous Mode Autonomous Mode is entered from Normal Mode if more than 4 minutes have passed since the processing of the last command from the ground After 2 minutes without command a warning is issued Autonomous Mode is left if any command is received The microcontroller will monitor constantly pressure and temperature control the pump and valves automatically listen for commands from the ground record data packets from the pressure and temperature sensors at a standard interval of 10 s and transmit them to the ground store part of these packets in EEPROM memory determine whether the floating altitude has been reached by monitoring time and pressure control the heating elements automatically control pump cycles automatically to prevent pump overheating 23 e store a status packet together with a data packet in EEPROM memory if a status change occurs Whether the floating altitude has been reached will be determined by com paring the current pressure and time with predefined values If the time threshold has been passed or if the pressure has been below its threshold value for at least 2min another warning message will be transmitted Af ter additional 2 min the valves will be open
17. as simple as possible using standard hardware a computer notebook and both standard and custom made software The interface between between the experiment on the balloon and the ground station is realised through the E Link connection If possible and available a simulation of the Esrange E Link should be part of the EGSE 5 1 2 Hardware Description A standard notebook or a standard PC with ideally two serial ports for redundancy reasons and a replacement unit both running WindowsXP A USB serial converter as a backup No electrical stimulators will be used during check out 5 1 3 Network Interface A RS 232 connection to the E Link ground unit operated at 9600 bps or higher hardware flow control 1 start 8 data 1 stop bit Can otherwise be suggested by Esrange 5 1 4 Software Description amp User Interface Stratospheric Census can be controlled from the ground either by a simple terminal program or by the Stratospheric Census Groundstation software This software is written in the JAVA language and visualises the incom ing data and status packets Additionally this data is saved in a log file Commands are easily executed via simple command buttons Experiment Commands the response status packet and or OK is displayed The cur rent status of the connection to the experiment is shown Up Downlink If a mission critical command is issued the operator will be asked to confirm the command in a dialogue box 99
18. be determined by experiment 3 4 Power interface requirements 3 4 1 General Interface Description For the electronic components two potentials are needed namely 12 V pump actuators heaters and 5 V control system The 12 V potential is achieved by placing three batteries 3 6 V 13Ah SAFT LSH20 in series forming a potential of about 10 8 V This simplifies the design because a regulator for these components can be omitted However verification of full functionality has to be done For simplicity this potential is denoted by 12 V in the following The 5 V potential is regulated down from the 12 V potential 3 4 2 Power Distribution Block Diagram and Redundancy Two battery packs are connected via diodes to have double redundancy A block diagram can be seen in figure 10 3 4 3 Experiment Power Requirements An overview of the power requirements can be seen in table 1 This table yields a total charge consumption of 15 45 Ah For total redundancy two 33 BATT 1 BATT 2 e EN gulator Figure 10 Power distribution block diagram 5 v strings for each battery pack are needed Fach of them has 3 batteries Thus a total of 12 batteries is needed Compo 1 Povver Potential Current Duration Charge nent W V mA h req Ah Control 2 5 0 4 10 4 System Regulator 3 10 0 4 10 3 Heater 5 10 0 5 5
19. chapter In addition single components of the electronics might fail 1 The power supply connection might fail This risk is kept low by hav ing redundancy strings of batteries connected via a diode to the other battery packs 2 If the pressure sensor fails the system can still be controlled by the ground station A double failure of the sensor and a connection loss might result in a complete failure of the experiment when it happens during critical phases i e opening and closing the valves 3 Failures in valves or pump might result in false conclusions drawn from the neutron activation analysis 3 1 1 2 Microcontroller Safety amp Risk of Failure No immediate safety risk stems from the microcontroller itself As the hear of the experiment in terms of controlling pump heaters and valves a microcontroller malfunction poses a high risk for total failure of Stratospheric Census e Loss of microcontroller power Problems with the microcontroller power supply can occur Temporary power loss leaves the chance of recovery microcontroller reset total power loss is fatal e Microcontroller in infinite program loop This is prevented by using the watchdog functionality very low risk e Wrong command interpretation Commands are secured with a check sum very low risk 2T e Temperature outside microcontroller operating range If temporary very low risk for the experiment If permanent possible loss of the experiment e Lo
20. eui IE H S I jdnueju au esy dn jas UOISISAUOI a y dn 199 MO NWUSUEIL pueuluo5 ejnoex3 jeuuou SPON Be 3 buruseMm 1989 o e1 unsx9ayo asied yes idnu lul Lyvn uvn dn jos Be oiny 18819 dund eui yes pue NMd dn jas NOYA33 o eed 9 SNIEIS SUM dwnq 04400 S A EA 04UOO ony HO Burusem 39S 9 pues 1 6160 18819 Jexoed snes pues INOHd33 won senjeA sedulo2 en 2 Be 4oiny Jexoed eyeq pues Bopyoyem dn jas Bopyojem 18594 ony epo S19 29H 101002 EWION SPON enij2 1 uonezientul JeJ 041U09040I N HEIS ure 3 7 2 Design for Redundancy amp Shutdown The Autonomous Mode was designed to provide absolute independence from the ground station in terms of controlling the experiment Together with the fact that all data taken during Autonomous Mode is stored in memory this should make the mission immune to temporary up and downlink failures After the connection is reestablished all data recorded in the meantime can be sent to the ground For longer gt gt 30 min up and downlink failures not all data can be stored due to finite memory capacity In the case of a temporary power shutdown the microcontroller will re cover on its own albeit the data stored in SRAM will be lost The microcon troller watchd
21. po dude nud A PUB excu b ide awe e qe e s B Revisions C Outreach Programme 55 99 99 99 99 99 96 96 58 58 58 59 60 60 60 61 61 61 61 61 61 61 63 63 65 65 68 69 71 mN Q H H Scientific Analysis DI Stratosphere D 2 Stratospheric dust D 2 1 Dust profiles D 3 Location specific considerations oce cx xe D 3 1 Geography and climate rete erret dents D 3 2 Balloon Trajectory Full component list Gantt chart Abbreviations Bibliography 72 72 72 73 74 74 74 77 81 83 85 List of Figures QO Ot i gt ND NN co OO 1 Ob OG Qo Schema for the information flow 12 Epcos thermistor performance 13 Sketch ob the pipe te pa a Pa FR AA 15 Structural design of the experiment 16 Diaphragmrf ups qom Jr siete ete he e te eS 19 A preliminary design of the filter 21 NIC DE drawing a ek eae aio e eck 31 Drawing of the connection to the gondola 32 LSH 20 performance ae E s 32 Power distribution block diagram 34 Connector diagram ih gee SES Se ds 35 Small vacuum test chamber 51 Small thermal test chamber oaoa a 52 Ground station user interface 56 Ground Control Instructions Table 57 PCB during soldering
22. the team program and assemble the experiment at IRV in Kiruna Sweden e Mission Phase The actual flight campaign in October 2008 e Recovery Phase The filter has to be recovered for analysis This is handled by Esrange 60 e Analysis Phase The filter is extracted under clean conditions and sent to partner institutes contacts available for dust analysis 6 3 4 Current status 6 3 4 1 Mechanical Engineering The hardware components have been delivered to the team members and assembly has started 6 3 4 2 Software Engineering The microcontroller has been pro grammed according to the flow diagram in the CDR document Its operation will now be tested and optimised on a model of the PCB once it arrives The ground station software is due to be finished at the end of August 6 3 4 3 Electronics The PCB board design has been finished after ini tial tests had led to changes It is scheduled to be tested with the microcon troller Figure 16 PCB during soldering 6 3 4 4 Pump amp Filter The pump has been delivered and will be tested in Kiruna in September see section about Testing 6 4 Configuration Control All changes in the hardware or the software are discussed within the team and reported in the bi monthly progress reports 6 5 Deliverables As mentioned in section 6 2 the group will provide a progress report to the course supervisors around twice a month A PDR has been delivered to IRV 61 at May 8th 2
23. 008 as noted in section 6 3 2 The SED is a continuously growing document which initial version was a project proposal and which grew to a PDR and a CDR A Flight Readiness Review FRR will be carried out September 23 at IRV The group will bring two computers and corresponding cables to run the ground station 62 A Electronics A 1 Circuit diagram 63 urelgerp JIMIN oruo1329 4 T AMSTA ODA iojoeuuog xo e 1 Hz e LE 220 nor 29A Josueg eunsseig WO ar sad Tee stoxasy im TN ON Fx 1SdS 84 MS 5 ND ON S ye 7 A ON 2 ov DON Cea SALON ET A T id vor 1NOG ODA ozo mad ales ejes se ses tels es L ikziki Esp dhan pps pne n Y da g 2b ue 6 28 205 S gt r acid i 3 TOXL Cat 3 or saga pox KSE i a z EC ANE Y DE ve 20Av sa Hi 9 ol I ano tad L 1106 N T lo E k 2 oH zad Fr ow 15 wo d oad Fey 3 e d Yad ON FG IS a La ODA 1MOS VOPGZOM T
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25. 1 apow snowouojne 40 3WN 3J4NSS34d syuawesinbas Ajipow pueuuo gt 0O13H pues pepeeu se jjo uo 133834 YIIMS T 02 aBeyon dund eseaabur Sbued payloads apismo eunjeaeduiei plod 03 duin yulluMop pue dn 2242 eJnje1eduua s iuo43 e e abueyo eJnjeqeduue dund esiej AT 03 Sbeyjon dund eseau ap joy dund dund samo dund aseadap 9AJBA A93YI eso 006 A PA I 195 dund aseaioul AIRIS 195 193Yy9 u do We epninje buneoy jueuuuedxe dos 3yu uuli dx Wes 0012 uonipuo5 JuswusImbang SEL Table 10NS Ground Control Instructi Figure 15 57 6 Project Management 6 1 Organisation and responsibilities The team of Stratospheric Census consists of five ambitious students four from Europe and one from Australia all studying in the ERASMUS Mundus Master Program Space Science amp Technology Spacemaster We have experience in the design of balloon payloads through a CANSAT satellite in a drinking can competition in the first semester of the study programme We are e Mark Fittock from Australia His main responsibility is the mechanical structure of the experiment He has experience in mechanical engineering e Gerrit Holl from the Netherlands His main responsibilities are the theoretical and scien
26. 5 Alan C Tribble The Space Environment Princeton University Press revised and expanded edition edition 2003 87
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28. Corporation SSC Between April 20 and April 26 a training week was organised at Esrange during which all groups including the Stratospheric Census group in both the BEXUS and the REXUS campaigns presented their PDR s and discussed those with a panel of experts from ESA DLR SSC and SNSB Eurolaunch Eurolaunch is a cooperation between DLR and SSC Euro launch organises and pays the launch of the BEXUS 7 balloon ESA ESTEC The European Space Agency ESA is heading the BEXUS campaign and sponsoring the project by funding the balloon flight ESA also hosted the selection workshop in March 2008 at ESTEC Noordwijk The Netherlands IRF The group is close to the Swedish Institute of Space Physics IRF and will use some resources available at the IRF for assembling parts of the experiment 6 3 Schedule and Milestones Those who fail to plan plan to fail Unknown After Stratospheric Census was chosen for flight the necessary tasks required to finish the project in time for launch were identified Rough estimates for the duration of each task were made and a main responsible assigned The Gantt chart in Appendix F estimates the overall project duration This chart was and is continuously updated and the project progresses Tasks that are already fully completed dark are shown with their actual start and end date Not yet completed tasks light are shown with their planned start and end date Sufficient time was all
29. EREECHEN 61 Electronic circuit diagram NG 64 Grounding diagram rana vene x EE 65 POB aree strive y fec conte Atala ra ae Gard 68 A screenshot of the front page of the website 71 Size distribution of stratospheric particles at an altitude of 18 t0 20 Jm Some cay es dod os 76 List of Tables Ob ND 10 Power requirements o Lin ceto dome ske 3 00 34 Experiment OBDH Interface Channels 36 Outgassing estimates sp te Sw Ve 44 Experiment test matrix so a Ae A ah ee da ler 47 Table of revisions im e o ea es baa atone te Bf dn p 70 Power B dget 4 2 3 aue S AG ee da F ke ala 80 The mass budget for the Stratospheric Census Experiment A conservative estimate for the total mass is 8 kg allowing for Somezadditi ns elo bs e Boe Ss oo a que 80 Table of used acronyms _ HER Ser 84 1 Introduction Balloon flight campaigns especially BEXUS do not only bring us a little closer to space they also provide unique insight into the environmental con ditions in the Earth s stratosphere The stratosphere is an atmospheric layer just above the troposphere in a height of approximately 10 km to 50 km One of the most interesting stratospheric environmental conditions is the prevalence and nature of stratospheric dust Stratospheric dust is dust from volcanic eruptions dust stemming from outer space or dust of human origin and it has an influence on the world clim
30. I DDA T 2 CS IT 2 2 S AND H vl 27 ova isa H d e va eg 564 4 GET wa men saa at Te ovd i ce DE ODA isl E id lo x 2 27 Ls goo se H Bi 92 t m ur 15 7 00 vad Zil z LE 1 LEE I mm 1 ai ssi A CR ale z ul T w 1 1 af ANN X vor R wo 4 oed e 4 Lowiawnd ODA awa vi d D D d ml 64 A 2 Grounding diagram bal uns Temp Sensor Battery Aluminium structure Gondola Structure structureless units Figure 18 Grounding diagram A 3 Pin allocation Interface pine Configuration Pin Allocation 4 pol 1 Vie 12 V red POW 4 2 GND blue 3 not used 4 not used 65 ACT 6 pol DIN 45322 Valve 1 two way yellow Valve 1 two way purple Valve 2 three way green Valve 2 three way white GND blue Ve Pump 12 V red RS232 3 pol DIN 41524 RX TX GND 66 TEMP one un used 7 pol Temp Sensor 1 green GND blue Temp Sensor 2 white GND blue Temp Sensor 3 purple GND blue unused ACT feed back 6 pol DIN 45322 Switch 1 Valve 1 blue Sw
31. M Pump M F M M Filter M Sensors M F C Total M M F A A A A Table 4 Experiment test matrix M stands for Measurement A is Accep tance C is Calibration and F is a Functional Test Details on all tests can be found in the text 47 importance for not harming the surroundings see section 2 3 3 6 for details on that 4 2 1 Microcontroller Testing Microcontroller qualification testing can be structured into the following parts 1 Test of operating modes and operating mode switching 2 Test of sensors 3 Test of memory management 4 Test of heater control 5 Test of pump temperature control 6 Test of valve control 7 Test of Autonomous mode experiment control 8 Test of commands and communication link 9 Test of command parsing command rejection and CRC checksum pro cessing Most of these are simple works does not work tests However for heater control pump control and the Autonomous mode experiment control in general the test of the microcontroller code has to happen in conjunction with temperature and pressure simulations This way the reaction of the control loops can be checked 4 2 2 Microcontroller Qualification Requirements The microcontroller is qualified for flight if it 1 has full functionality 2 successfully passes a long term running test at least 5h in Normal Mode 3 successfully passes a long term running test at least 2h in Au tonomous Mode 48 4
32. Try different operating voltages find the voltage that gives a stable temperature Observe the inside temperature of the box containing the electronics Especially monitor the temperature of the MOSFETs 51 4 2 4 1 2 Acceptance Criteria The pump works under strato spheric pressure conditions It can be operated at a voltage that gives sufficient throughput of air without overheating the pump The throughput of air can be extrapolated it does not have to be measured Sufficient throughput of air is defined as the amount of air 4 2 4 2 Thermal Test A thermal test under ambient pressure conditions will be run for the operating pump and for the complete experiment in the cooler heater shown below Temperatures of 60 C can be reached 3 31 Figure 13 Small thermal test chamber 4 2 4 2 1 Test Procedure e Test the pump at 0 C with regard to its general behaviour e Cool the pump to assess at which temperatures it can safely be restarted e Cool the experiment without the pump to 50 C or lower and check for any ill effects 4 2 4 2 2 Acceptance Criteria The pump works satisfactorily at 0 C and ambient pressure It can be restarted at OC after it has been cooled to lower temperatures The experiment shows no ill effects at 50 C 52 or lower The inside of the box containing the electronics should remain in a temperature region where electronic temperature compensation fo
33. acuum chamber was rapidly reduced to 40 kPa No bursts of components were detected and all soldering spots remained faultless 4 2 3 2 Batteries The batteries will according to their manufacturer lose or gain performance depending on there temperature see figure 9 The passive thermal control system must be tested with batteries working at full load Preferably the temperature should be kept as close to 70 C as possible Means of finetuning the design are thermal wrapping or thermal paste 49 4 2 3 2 1 Results of battery thermal test The thermal battery test was performed by placing one battery in the thermal box This battery was fixed with insulation foam A current of 1 A was drawn out of the battery During this no extraordinary increase in temperature was measured From this it can be concluded that no thermal paste between the batteries and the box will be necessary However the system will behave differently in vacuum and for that reason a temperature sensor is placed on the batteries 4 2 4 Pump Testing The pump KNF Neuberger N89 KNDC 12V has to undergo the following test procedures 1 2 8 Basic functional tests immediately after delivery Air flow measurements under ground pressure conditions The curve of airflow vs vacuum pressure see datasheet 16 should be reproduced if possible Air flow measurements under stratospheric pressure conditions The same test as in 2 performed in a vacuum chamb
34. ainless steel was chosen As per the requirements of the pump 16 all loads are on the suction line In order to run the pump at a low speed to avoid seizing two inlets are available to the suction port of the pump that can be switched using a 3 way switching valve couple to an electric actuator The primary initial line begins with a simple valve as shown below in figure 3 This valve s function is to stop contamination of the filter during the ascent and descent of the balloon to ensure that the dust collected is all stratospheric The filter assembly is connected between this valve and Valve B so that both valves and the filter can be removed to avoid contamination when removing the filter for analysis This is connected by a short length of pipe that will be used for any sensors necessary to monitor the flow to the pump via an adaptor The collection intake line is a straight pipe from the exterior of the gondola so that the pump can draw a small quantity of air through the system This is to allow the pump to operate at low speeds during the ascension of the 14 balloon avoiding the possibility of seizure The inclusion of a valve at this point was necessary in any case as it must be possible to isolate the filter for removal at the end of flight The exhaust is simply released into the gondola s interior as it will not disturb Stratospheric Census or other experimenters apparatus Figure 3 Sketch of the pipe Figure
35. ate Our project therefore aims at performing a census of stratospheric dust A concept for a light and cheap filter probe has been developed this probe shall be flown to this atmospheric region of interest and be recovered for laboratory analysis 1 1 Overview The document structure is based on supervisor guidelines Here follows a brief overview of some of the elements of the document This overview is far from complete please refer to the table of contents for a complete reference of the document contents After the introduction the core experiment is described in section 2 The scientific goals are outlined in section 2 1 and the experiment is sum marised in section 2 2 Then follows a description of all hardware elec tronics pump filter structure in section 2 3 and software in section 2 4 Section 3 contains all interfaces and design requirements Of particular importance here is section 3 1 1 on fault tolerance design and section 3 1 2 on safety In section 4 verification 4 1 and testing 4 2 are discussed The ground station in discussed in section 5 The rest of the document is concerned with information related to man agement section 6 The first appendix appendix A contains various diagrams relevant to the electronics Secondly appendix B contains information about major document versions Appendix C consider the outreach programme Ap pendix D contains scientific background i
36. aw W size distribution functions Figure 21 Size distribution of stratospheric particles at an altitude of 18 to 20 km Source 23 76 E Full component list On the following pages are component lists for the financial budget the mass budget and the power budget TT 78 DS SEET WAS D T AT P T 8 c8 ur 70 98 81 eyd ureog PIA IV GIG Das Das I 99 12P 87 eyd 91 suog Z AH OE TT OS TT I 6000 170607 01399105 QUIBIH 01499105 103 9IN SINN PIA 0070 00 0 I HIN9 80 S8L SS YOTESEMS GO z T 19945 ss yure s odtq PS ZL PS Z I TI DTP SS A0 9BEMG 9995 sse utej3s DAJLA Lem z 9I9AHO 2168 T 89 I A IXDTP SS YOPER EMS 19935 sso ure3s oaea em e OTOATTO 1911 1911 I 2 0S S Ld SIN YOTESEMS yuepeos PLOIYL otqo1oeuy pe1eAT op 9 8 698 1 2 SUZ V Z SS yopesems LAJ 48 1 99 LAN 8 I 19998 ss rure s z depy SITUBUIIIN 000 000 c ODIBUIH ioprdsoueN rew UN OTOATTO 00 0 0070 I sy 4142 JO OIJUODOIDHA m preogp gumin D Z AH P 09 5 29 0 g 02244 961696 UIS 19H 9I9AI 9 06 0 60 0 OT UO MST 0 JON 1606666 Sule UO _104s1s0Y Z AH 00007 00 09 8 OG HST Yes V N Ug ouxosg u il b s rt 33egq D Z AT P 98 08 98
37. d Kurt M Marshek Fundamentals of machine component design John Wiley amp Sons Inc New Jersey USA 3rd edition 2000 Knf diaphragm pumps for air gases and vapors March 2003 J Ku era Methodological developments and applications of neutron activation analysis Journal of Radioanalytical and Nuclear Chemistry 273 2 273 280 2007 M Patrick McCormick Pi Huan Wang and Lamort R Poole Aerosol Cloud Climate interactions chapter Chapter 8 Stratospheric Aerosols and Clouds Academic Press 1993 E Mullane SS Russell and M Gounelle AUBRITES AN IRON AND ZINC ISOTOPE STUDY 36th Annual Lunar and Planetary Science Conference March 14 18 2005 in League City Texas abstract no 1251 2005 Bruce R Munson Donald F Young and Theodore H Okiishi Funda mentals of Fluid Mechanics John Wiley amp Sons Inc New Jersey USA 4th edition edition 2002 Elmarco nanofilter test results http tinyurl com 5ofvf6 Online accessed 11 April 2008 Olle Persson Harald Hellman and A Stamminger Bexus user manual Document ID BX00 07 12 11 BEXUS Manual 4 4 doc December 2007 RG Pinnick JM Rosen and DJ Hofmann Stratospheric Aerosol Mea surements III Optical Model Calculations Journal of the Atmospheric Sciences 33 2 304 314 1975 JM Rosen DJ Hofmann and J Laby Stratospheric Aerosol Measure ments II The Worldwide Distribution Journal of the Atmospheric Sci ences 32 7 1457 1462 1975 86 2
38. e id 6001 2007 Detection limits for specific elements nuclides http web missouri edu umcreactorweb pages ac_pertable shtml Online accessed 19 May 2008 L Elterman R Wexler and DT Chang Features of tropospheric and stratospheric dust Appl Opt 8 5 893 903 1969 Jens Laursen et al Sadface final report Technical report Institute for Space Science Kiruna 2007 Farnell b57540g303j epcos thermistor ntc 30k http tinyurl com 59emom Online accessed 13 April 2008 DJ Hofmann JM Rosen JM Kiernan and J Laby Stratospheric Aerosol Measurements IV Global Time Variations of the Aerosol Bur den and Source Considerations Journal of the Atmospheric Sciences 33 9 1782 1788 1976 DJ Hofmann JM Rosen TJ Pepin and RG Pinnick Stratospheric Aerosol Measurements I Time Variations at Northern Midlatitudes Journal of the Atmospheric Sciences 32 7 1446 1456 1975 RD HUDSON and EI REED The stratosphere Present and future NASA 1979 Kjell Edmund Ims Modular Mechanical Platform MMP PhD thesis Umea Universitet Kiruna August 2005 85 13 14 15 16 17 21 22 23 Jan Jakubek Coincident analysis device version directly at ieap http aladdin utef cvut cz ofat Methods CINAA index htm Online accessed 19 May 2008 C E Junge C W Chagnon and J E Manson STRATOSPHERIC AEROSOLS Journal of the Atmospheric Sciences 18 1 81 108 1960 Robert C Juvinall an
39. ed and the pump started unless some ground station interaction occurs before The same procedure applies for the descent As it is difficult to judge when descent will happen pressure will be the only indicator for the stop of the experiment 2 4 5 Further Details Technical details on packet structure a complete flow diagram etc are given in section Experiment Software and Autonomous Functions section 3 7 2 5 Operation 2 5 1 Measured and calculated flight information The following is measured directly using sensors apart from the actual col lection of particles using the filter e Two temperature sensors one to measure the pump temperature one to measure the control box temperature This information is needed for heater and pump control e One optional temperature sensor e One pressure sensor to measure the ambient pressure This is used to assess whether the experiment should be started 2 5 2 Location in the gondola Because of the nature of the experiment it is highly essential that the exper iment is closed to one of the sides of the gondola That leaves the choice of the viewing direction up down or to the side It is expected that contami nation would be lowest if the viewing direction for our experiment is straight down see the section on contamination 3 9 below For that reason the preferred viewing direction is straight down 24 2 5 3 Pre flight procedures In the last days and moments befo
40. ements apply Critical part of the control box is the pressure sensor which provides compensated data from 0 C to 85 C The battery box should be kept on a level as high as possible to 70 C Figure 9 to get maximum performance The pump specifications state that it will op erate between 5 C and 40 C However it has flown previously and operated 30 sup JOIN 2 910314 130 I 133HS EZ 31908 HOEM z WNIUILUNIV 7 r AVIJILYW vo O QAdav 19NDDJg 1004 80 50 61 weu HOW 3iva 38hIVNOIS 3WVN s3903 EE Ee SN3IJWITIIW NI 33 Y SNOISNIWIG Sa RIORUM anyangga 03410346 ISIMASHIO SSSINN P irdi 2 gt L C dIVOS V I si 1 2 8 a Cn o y SC 3l Figure 8 Drawing of the connection to the gondola without any active thermal control Due to the temperature fluctuations critical elements of the structure must take into account the changes in size 3 6 3 5 1 0 3 4 3 3 3 2 3 1 3 0 2 9 2 8 2 7 Cell voltage V 4 10 100 1000 10000 Current mA Voltage plateau versus Current and Tempe
41. er space simulator at 10 mbar The obtained curve airflow vs pressure can be used to for flow predictions Monitoring the pump temperature during operation under strato spheric pressure conditions space simulator If possible Monitoring the pump temperature during operation under stratospheric pressure conditions and cold temperatures Test of the vibrational spectrum of the pump This is to assure that no other experiments can be affected by these vibrations Test of electromagnetic interference of the pump with other electronic components Final operation test with all tubing attached in the space simulator The pump is ready for flight if it is in working condition and can be kept from overheating under stratospheric pressure and temperature conditions 50 4 2 4 1 Vacuum Test A vacuum test for the pump will be performed in a small chamber at IRF in Kiruna The small chamber was chosen due to its permanent availability The goal of the test is to assess if and how fast the pump might overheat under stratospheric conditions Figure 12 Small vacuum test chamber 4 2 4 1 1 Test Procedure Investigate in a pre test the hottest point outside on the pump during operation Mount a temperature sensor on the pump Mount the pump in the vacuum chamber Route power supply cables and temperature sensor cables out of the chamber Functional test Evacuate chamber monitoring the temperature of the pump
42. he possibilities of pump failure during flight the pump that was chosen has been previously tested in the stratosphere and seen to start and run in temperatures much below the specifications However if the bearings seize or another malfunction occurs flow will be limited or cease entirely The valve and actuator assemblies are both single points of failure but design decisions have been made to reduce this impact Critical failure will occur if the valves fail to open at the beginning of sampling However if failure occurs during sampling the valves should automatically switch back and protect the material collected from contamination If the valves freeze shut or open as the temperature rises again control will either be regained or they will automatically close In this way although critical failure can 28 occur if the valves can not be opened failure during sampling should not be fatal to the results of the experiment 3 1 2 Safety Concept The experiment does not contain any electro explosive devices pressurised containers or radioactive sources It contains batteries Batteries can be chemically hazardous when leaking but this should not happen The experiment contains a pump that causes vibrations and can thus cause problems for other experiments on or near the gondola A vibration test will be carried out to determine the frequencies as described in section 2 3 3 6 All mechanical parts comply with Swedish industry safety
43. heric dust in the northern hemisphere subpolar region e To measure during the campaign pressure and temperature of the ambient air In addition to the scientific objectives Stratospheric Census has the ed ucational objective to gain as students knowledge and experience 2 2 Experiment summary The main idea is to measure the stratospheric dust profiles by collecting air and pumping it through a filter during a balloon flight The pump that will be used is discussed in section 2 3 4 the filter choice discussed in section 2 3 5 To ensure that only stratospheric dust is collected the filter has to be sealed off by valves during the launch and ascent of the balloon Those valves are treated in section 2 3 3 1 Once the balloon reaches floating altitude they are opened and they are closed again before the balloon descends This process is controlled from the ground via a radio link E link Commands are sent by a ground station computer section 5 and received and executed by a microcontroller on the balloon section 2 4 In case of a radio link failure the microcontroller can work autonomously Various sensor data is downloaded from the balloon indicating the status of the experiment After the mission the received filter is extracted and given to post flight analysis section 2 5 4 The results will be published in a final report Parts of the experiment are Commercial Off The Shelf COTS compo nents pump val
44. iderably lower than in the lower troposphere so this may be a reasonable approximation If one assumes that particles travel straight paths relative to the balloon after outgassing one can estimate the amount of impacted particles using view factors Unfortunately this assumption cannot be made because the pump is actively sucking air from the environment The situation will thus be considerably worse It is difficult to estimate theoretically not only how many particles will diffuse from the surfaces but also how many of those will be caught in the air flow through the filter It depends on many variables many of them poorly known the viewing direction for the hose the distance to surfaces outgassing particles the path that those particles travel whether they fall down or float the sucking power of the pump from what distance such particles will be caught the presence of other experiments outgassing particles and probably a number of other factors The worst case scenario approach does not work either the worst case would be catching an outgassed particle big enough to block the valve completely this is probably a highly unlikely scenario A good knowledge of the profiles of stratospheric dust is required to be able to tell apart contamination from actual measurements in the neutron activation analysis Despite all this a very rough estimate is made The following sources of contamination are identified e The balloon
45. ily available and economic e There is less friction than in rotary vane pumps e A diaphragm pump has already been used successfully on a BEXUS balloon in the very similar SADFACE experiment 7 Possible disadvantages of diaphragm pumps e Depending on the material of the diaphragm it might become brittle in the cold and could therefore break Decision has been made to use the N 89 KNDC from KNF 16 2 3 5 Filter and Sensor Subsystem Payload 2 3 5 1 Filter requirements To get a meaningful detection the mass of the caught particles needs to make up at least 1 ppb parts per billion of the mass of the filter 19 An estimate of the relative mass of the particles M Nm nVm p n tm va 0 M Q 1 In equation 1 C is the relative mass of the caught particles is the sticking ratio considering the amount of particles that are attached to the surface of the hose or that fly through M is the total mass of the caught particles kg My is the mass of the filter kg N is the total number of particles m is the average mass of the particles kg n is the particle density m gt 3 V is the total volume of air sucked in m is the air flux 75 and t is the total time s in which air is sucked in If one estimates values for the different quantities in equation 1 one can estimate the relative mass If we take a 0 5 n 109m pu t 5hours m 1ug and mr 100g one gets a relative concentrat
46. in trace amounts The method is nearly free of any interference effects as the samples are transparent to both the probe n and analytical signal gamma ray CINAA is applied instrumentally no need for sample digestion or dissolution so there is little if any opportunity for reagent or laboratory contamination The team will focus on iron nickel and cobalt isotopes and will try to find out very spare ones of iridium and similar as well The team expects isotopes of those el ements Fe Co Ni originating from volcanic eruptions in slightly altered than naturally occurring well measured ratios Heavier nuclides are present as well 19 A main advantage of the CINAA is the possibility to distinguish terrestrially uncommon isotopes thus recognising them as of cosmic origin Among others Fe 60 or Ni 60 can be some of the clearest indication of an extraterrestrial source Also the Fe 57 Fe 54 relative composition differs strongly for terrestrial and cosmic sources 26 3 Experiment Interfaces and Design Require ments 3 1 General Design Requirements 3 1 1 Fault Tolerance Design 3 1 1 1 Electronics A risk of failure of the electronics subsystem must be kept as low as possible since a complete failure of the electronics would result in a failure of the experiment However a complete failure is unlikely due to excessive testing In the worst case the microcontroller fails This will be discussed in the risk analysis in the microcontroller
47. ion of m lug Dior ee 0005 hour 100g Of course all of the values are very rough estimates However the esti mated value is more than six orders of magnitude above the necessary value of C 1 107 so even if all of the values are much worse than estimated here it is still likely that we can detect particles The filter property that is relevant is really the flux divided by the mass If the filter is twice as heavy and the flux is twice as high the detection is in the end the same This does not take into consideration the contamination C 0 5 109m 2 2 3 5 2 Choice of filter High requirements must be served by the filter in order to catch dust particles down to a size small as 0 3 um Also the filter must not be affected by the low temperature neither should it allow water vapour to freeze on it and in that way degrade the filter The decision was made for the Nanospider TM Technology which was developed by Liberec Technical University Czech Republic and is now manufactured by Elmarco This type of filter consists of cellulose filtration material treated with PAG polymer nanofibers 100 to 500 nm in diameter During a test it was able to catch NaCl particles of 0 2 wm with an efficiency of almost 80 where particles of 1 jum were captured fully 21 Chosen filter with mass density of the nanolayer material of 0 19g m causes a pressure drop of 178Pa which requires the pump to build up a pressure which is more tha
48. itch 2 Valve 1 purple Switch 1 Valve 2 white GND blue 5V red Switch 2 Valve2 green The pin numbering for the connectors correspond to the pin numbering in the schematics apart from the ACT interface which on the schematics is numbered as follows Pin 1 Vcc pump 12 V Pin 2 GND 67 Pin 3 4 Valve 2 Pin 5 6 Valve 1 A 4 PCB DI ar get e ES SN FLA HI SN PB Ei SN PB Tu Li m Ro o a m 4 o 1 ERUNS 78 Figure 19 PCB 68 a 1 B Revisions A table of revisions is shown in table 6 69 Date Version Changes Preliminary Design Review 2008 04 14 1 0 Initial PDR as delivered to ESA 2008 05 05 1 1 Restructuring and various updates Critical Design Review 2008 05 19 1 9 Major restructuring 2008 05 26 2 0 CDR as delivered to IRV Mid term Report 2008 07 28 3 0 All brass components were replaced with stainless steel counterparts Provisions were made to save more status data in the on board microcontroller EEPROM on board backup Hardware assembly will start ear lier than initially planned Both the electron ics and the battery box are designed to be at tached with screws on the back side of each box Initially plans had been made for using check valves that close automaticall
49. itude of 20km 24 At Ice island at 85 N a concentration of around 1em was found at the same altitude Higher altitudes were not measured in this report at those latitudes Size distributions are given in 23 The size distribution is almost constant with altitude A best fit function to the size distribution between 18 and 20 km altitude based partially on measurements by 23 is given in the same paper Ny fa ME a Ni gt sl exp 22 dr 3 In equation 3 No 10cm o 1 86 r 0 0725 m Refer to 23 for a discussion of this equation One of the lines in figure 21 is a graphical representation of this In 9 is reported that the concentration of sulphur above the tropopause is between 0 1 and 0 3 ppbm parts per billion mass There also exist Aitken particles particles that are smaller than 0 1um in diameter Those are not feasible to detect using the detection method because available filters do not catch such particles Therefore we will not consider such particles D 2 1 Dust profiles Under normal stratospheric circumstances the bulk of aerosols can be ap proximated by droplets of 75 H2504 and 25 H20 18 Volcanic eruptions increase the amount of dust considerably but the profile is still mainly sul phur since this is the origin under normal stratospheric circumstances as well 73 Key issues in estimating the amount of cometary dust one might ex pect to find in the stratosphere are the survi
50. kbyte of data 1kbyte is reserved for status change packets and their corresponding data packets the remaining 3 kbyte are for the saving of data packets during autonomous mode can be sustained for 30 min until old data has to be deleted Al 3 8 Electromagnetic Compatibility Requirements 3 8 1 General EMC Requirements Radiated emission will be kept as low as possible using filters for outgoing connections and shielded wires for pump and external sensors The main part of the electronics is placed in a metal control box The design is sufficient also to reject interference from outside the experiment 3 8 2 Specific EMC Requirements The external temperature sensors form a high impedance line susceptible to picking up noise Apart from the above stated electronical action taken the software will compare several measurements to filter out incorrect measure ments 3 8 3 Grounding In addition to grounding the experiment in itself it is grounded to the gon dola This is inevitable since a connection between the control box and the E link has to be established A grounding diagram can be found in figure 18 in appendix A 2 3 9 Cleanliness Design and Contamination Control Requirements Particles in the stratosphere can be of volcanic extraterrestrial or anthro pogenic origin A particular case of particles from anthropogenic origin are particles that originate from the balloon the gondola or its payload in cluding the own e
51. lective responsibility for the verification of the whole system 4 1 3 Verification by Analysis All subsystems are checked and double checked before the final building so that errors in the design can be identified as early as possible 4 1 4 Verification by Test Testing is a very important part of the design of any experiment partic ularly if this experiment is outside reach after launch such as is the case on a Satellite rocket or a stratospheric balloon Thorough testing is thus necessary 4 1 5 Verification Control System 4 2 Experiment test matrix Tests can be divided into tests that verify that the own experiment is working and tests that verify that the experiment is meeting the requirements for flight e g not harming others and not harming the flight train After all the parts have been tested individually see the following sections the parts will be put together and the whole system will be run to check that the pump and the valves are working correctly The vibration test is of particular 46 2 S 25 8 p S 2 a D 2 2 2 D o 02 o Si E S 2 ag Sun Q ols o ial E EE E salt a FA iiz a 212 2181412 8 2 al Gu S a S ol m 5 ES ns Ole uw A el g 02 19 yo o Q y o 02 a o R I o o e SS S SE ie z s Experiment uit gt E m n n Am 3 m O E Control box MIM M F Battery box M M
52. mp The pump is controlled by the means of PWM Pulse Width Modulation to allow the setting of a specific voltage At the beginning of operation it can therefore be run at a lower speed During the campaign the number of cycles is then be increased step wise if pump temperature risk of overheating permits The heating elements are controlled automatically by the microcontroller with reference to a threshold temperature However they can also be con trolled manually from the ground if need arises Data will be stored in two different packet configurations data packet containing dynamic data i e temperature pressure and time and status packet containing data about pump valve heater status and operating mode Data packets will be sent every 105 status packets upon ground station request or when a status variable changes Based on these qualitative requirements the operation of Stratospheric Census is structured into three different modes defined in the following sec tions 22 2 4 3 Normal Mode Ideally the experiment will be in Normal Mode for the whole mission dura tion Prerequisite for this is a working up and downlink The microcontroller will then monitor constantly pressure and temperature generate data packets from the current pressure and temperature at a standard interval of 10 s and transmit them to the ground expect an OK from the ground after every packet to assure that up
53. n two times larger than ambient pressure 20 Figure 6 A preliminary design of the filter The team will acquire two identical filters and compare a filter which has flown with a filter which has not flown when doing the analysis 21 2 4 Software Overview 2 4 1 Computer Systems amp Data Storage Stratospheric Census will be equipped with a microcontroller ATMEGA128 CAN sponsored by chip45 It provides 4kB of non volatile EEPROM and 4kB of volatile SRAM memory Within the control box where electronics and microcontroller are housed a temperature sensor will monitor the thermal conditions A heating element is provided to assure that the temperature stays within the operating range of the ATMEGA128 from 55 C to 125 C It can be switched on as needed 2 4 2 Qualitative Software Requirements The experiment is launched with the filter valves closed and the pump oper ating at a low speed During the ascent of the balloon temperature and pres sure are recorded and transmitted to the ground Once the balloon reaches its floating altitude the filter valves will be opened and the pump cycled up with a command from the ground However if the uplink is not operational this should happen automatically if pressure drops below a certain level or if a certain amount of time has passed since launch Once the balloon leaves the floating altitude this process has to happen in reverse order Close the filter valve switch off the pu
54. nents of Stratospheric Census It is required to operate under the conditions prevalent in the stratosphere that is temperatures down to 90 and pressures of 10 20mbar Under these low pressure conditions a medium vacuum the lack of convective cooling also poses the risk of overheating At the same time power consumption should not exceed what can easily be provided with batteries and the pump should be light and small while still providing the necessary throughput of air Typical candidates are therefore vacuum pumps designed for the medium vacuum range defined from 3 kPa 30 mbar downwards Usually these pumps are designed to produce a vacuum against atmospheric pressure For Stratospheric Census the pump will work against the ambient medium vacuum which should have a positive effect on the possible throughput On the other hand the low temperature has a negative effect on the throughput as the molecules will stick to surfaces much longer at low temperatures 18 A Quum Figure 5 Diaphragm Pump 2 3 4 1 Pump types For a medium vacuum the most used and reliable type of pumps are rotary vane and diaphragm pumps The team of Stratospheric Census decided to use a diaphragm pump figure 5 for the following reasons e Diaphragm pumps are dry pumps they do not outgas oil e The diaphragm itself insulates the air stream against contamination from the rest of the pump e Diaphragm pumps are reliable read
55. nformation on the mission A full component is shown in appendix E This includes budgets for mass vol ume and cost A Gantt chart is shown in appendix F Finally a list of abbreviations is shown in appendix G The document concludes with a full bibliography 1 2 Acknowledgements and sponsors We would like to thank the following people organisations and companies for their support IRV for providing financial and other resources IRV staff for their time and effort IRF for the opportunity to use resources available there Esrange for giving us the opportunity to fly on a balloon The personnel at Esrange for their time and effort All members of the review panels for their valuable advice Eurolaunch Swedish National Space Board European Space Agency Progressum for financial support Elmarco for providing the filter Chip45 for providing the microcontroller Tommi Juopperi for his significant help in designing the electronic circuit 10 2 Experiment description 2 1 Scientific Objectives The key mission objectives of Stratospheric Census are e To design and develop a simple yet powerful concept of collecting dust in the stratosphere To collect stratospheric dust during a BEXUS campaign using a filter and to recover the filter sample e To use different techniques of analysis in particular neutron activation analysis and electron microscopy for assessing the relative frequency of elements in stratosp
56. ns the longest length of the frame was used for buckling cal culations 300 mm The max force that could be withstood before buckling occurs was calculated using TEI Fhuckt 2 N Where E is the Young s Modulus of the material I is the second moment of inertia and l is the length This gave a value of 110 kN for the max load before buckling Due to the reasonably short length compared to profile 1 0143 m3 In order to find a critical loading limit the plastic limit of the aluminium was found so that it could be compared with the buckling limit Fplastic Es E LN Where the cross sectional area was approximated from the density of aluminium and the weight of 1 metre of the bar Using a plastic limit of 270 MPa for this bar as was selected by 12 page 17 the maximum load was found to be 69 KN Comparing this to a rough force estimate of 8 kN by using 10 kg at 10 g as defined by with a shock factor of 2 15 page 280 and a safety factor of 4 15 page 263 shows that the structure will be able to withstand particularly brutal shocks caused by malfunctions of the balloon system This is important where the sample collected during flight is particularly vital to the success of the flight 2 3 3 5 Flow Analysis In order to verify that a pump selected would be sufficient to overcome the pressure losses caused by the pipe system simple 17 fluid flow calculations were conducted The head losses of the two inlet lines were c
57. nside the control chamber drops below a certain threshold the resistor network is switched on by the corresponding MOSFET Six resistors are put in parallel each of them providing 24V 680Q 0 85W of heat 2 3 2 6 Risk analysis Please refer to section 3 1 1 1 for a safety anal ysis of the electronics subsystem 2 3 3 Structure The structure that will support all the experiments components will be con structed from aluminium This material was chosen because it is light stiff and easy to work with This choice was also supported by IRV as they have considerable stocks of aluminium plate and rod The design of the structure will be developed now that all other components have been selected 2 3 3 1 Pipe substructure The pipe substructure of Stratospheric Cen sus comprises of three line connected to the pump The pump that we have chosen the process of which is described in sec tion 2 3 4 has two BSPP 1 8 ports Although this diameter is suitable for the system finding suitable components that would connect directly proved difficult and for costs sake it was decided to use simple adaptors to switch to 1 8 NPT connections By using this small diameter there is greater risk of the filter being plugged by particles however due to the low concentrations this should not be a problem By staying with this line diameter there is also the added benefit of weight reduction compared to earlier design iterations For all fittings st
58. ocated for overall system testing while each compo nent has its own test period as well Milestones are the PDR the CDR the end of the semester and the delivery to Esrange in conjunction with a flight readiness review 59 6 3 1 Planning of Phase D As this CDR report marks the end of phase C Detailed Definition phase D Production Ground Qualification Testing can be begun It includes the assembly steps in particular assembly on the clean bench that has to be prebooked The team has decided to assemble parts that might be harmed by contamination as late as possible to avoid any needs of special storage The main testing campaign is planned mid September using the IRF space simulator subject to pre booking Note that the different parts themselves are already tested before individually This is also to assure that they match the expected quality e g the pump performance and to be able to return them if need arises 6 3 2 Important Dates e April 14th 2008 PDR deadline ESA e May 8th PDR deadline IRV e May 26th CDR deadline IRV e June 2nd CDR deadline ESA e June 15th End of the semester at IRV e July 28th MTR e September 8th EAR e Flight Readiness Review September 23 e October 4 October 10 Launch campaign e January 15th 2009 Experiment reported handed in at ESA 6 3 3 Mission Phases The Stratospheric Census Project is divided into the following phases e Production and Testing Phase The members of
59. og will guarantee a reset in case of an accidental infinite loop in the code 3 7 3 Pump Instrument Operating Modes The pump can be operated at different speeds depending on the supply voltage This supply voltage is controlled by the means of PWM and a MOSFET In order to avoid a pump start in the stratosphere the pump will be in a low cycle operating mode during ascent and upon reaching the desired altitude will be cycled up to full speed as temperature permits Once the experiment is started valves open the pump voltage is slowly increased to 12V 1 V per minute monitoring the temperature Should the maximum temperature be reached the voltage is lowered again until a stable and thermally acceptable working point has been found The details of the control loop have to be determined in a thermal test For Autonomous Mode it will be based on safe and conservative assumptions 3 7 4 Packet Definitions Data packets and status packets have a length of 15 bytes including a CRC checksum byte to assure data integrity and a timestamp from the real time counter A data packet and a status packet are saved in the EEPROM after a status change A status change can be switching the heater on off changing the pump cycle etc In Autonomous Mode data packets are also saved periodically the interval dependent on memory consumption Assuming a data taking rate of once every 10 s the 4kB EEPROM on the ATMEGA128 could save da
60. ompared and it was clear from inspection that the line with the valves and the filter would cause a larger pressure drop From limited information supplied by Elmarco it was found the loss co efficient for a one layer filter albeit thicker than the one we selected was equal to 1 64 Through concern for the possible blocking of the filter from ice particles despite a low probability a value of 10 was used instead for the filter The loss coefficients of the entrance valves and connector were calculated using the approximations from 20 table 8 2 page 289 figure 8 22 page 482 Using the Properties of the U S Standard Atmosphere 20 page 834 and the filter approximation the pressure loss was calculated to be 0 17 Pa using 20 equation 8 36 This is well below the pump performance in atmosphere a pressure difference of 9 mbar from 16 However the pump will not operate to these standards at the low temperatures and pressure that it will be subjected to rigorous testing will be required to ensure that the design is sufficient as detailed in it s testing section 4 2 5 2 3 3 6 Vibration Analysis Vibration analysis will be conducted by testing after the experiment has been assembled This information will be shared with other experimenters using the same platform and if the amplitude or frequency are likely to cause problems vibration mitigation methods can be investigated 2 3 4 Air Pump The pump is one of the most crucial compo
61. ourse be happy to participate in any outreach effort that ESA plans within its own public relations framework 71 D Scientific Analysis Relevant questions for analysing the scientific relevance of the mission are e How long will the flight take e What is the geographical extent of the flight e What altitude will the balloon reach e What is measured e What can be determined from the measurements e What is the composition of the Earth s atmosphere at the altitude at which the balloon is flying e What are the environmental conditions within the balloon gondola e What are the constraints imposed upon the experiment by the gondola bus and the other experiments on the gondola D 1 Stratosphere The stratosphere is the atmospheric layer extending from the tropopause to the stratopause It is roughly the area where temperature increases with altitude The composition is very similar to that of the troposphere with nitrogen and oxygen being the dominant elements The most important difference in the chemical composition is that where the troposphere has a significant amount of water the stratosphere is very dry particularly at polar latitudes The mixing ratio for water has been measured to be between 1 and 3 parts per millions mass at polar latitudes on the northern hemisphere at an altitude between 15 and 20 km 11 D 2 Stratospheric dust The first major study into stratospheric dust also known as stratospheric aerosol
62. r the pressure sensor is provided i e between 0 C and 85 C 4 2 4 3 Thermal Vacuum Test A thermal vacuum test can be carried out in the Space Simulator at IRF in Kiruna The Space Simulator was not chosen as the prime testing facility as it cannot easily be controlled to stratospheric temperatures and pressures Still a test run without any criteria is planned provided that the evacuation and cooling process can be stopped around stratospheric conditions 4 2 5 Structural Testing The frame will be tested under a series of conditions to makes sure it is adequate for the full operating range 1 Static load test to be done for a load of 20 kg to represent shock condi tions Will be applied for buckling and bending of the frame structure 2 Shake test to be conducted using the facilities at IRV The shaker will be used to conditions as specified by Esrange This will include all components so that the effectiveness of the electronics and mechanical structure in shake conditions can be seen 3 Vibration testing will be conducted to investigate the vibrations in duced by the pump s motor The motor will be run until vibrations be come fully developed and the amplitude and frequency will be recorded The structure is deemed to be adequate so long as it does not fail under the static loading test The shake test will determine whether the electronic construction and brackets are sufficient during operation 4 2 6 Full functional test
63. racket that will be used to attach the frame to the base Four of these will be used to connect the frame to the structure These can either be connected to the inside or outside rails of the frame at any point along their length 3 2 1 Accommodation Requirements This total frame requires 350 300 200 mm before including the brackets for attaching this to the gondola floor These brackets can either be attached on the inside face of the frame or outside depending on convenience and volume restrictions The 300 200 mm face must face downwards and have access to the at mosphere in order to take samples whilst minimising contamination Apart from this the design has been made to be highly flexible as is desired for a case where arrangement changes may need to be made close to the launch 3 2 2 Attachment Concept and Foot Pattern In the name of flexibility the attachment concept has been kept as simple as possible The advantage of using a frame with rails allows the use of brackets that can be attached anywhere along the length of the frame Both balloon gondola possibilities use M10 bolt connectors but it is unknown yet how far apart the bolt rails are inside the gondola The bracket and bolt arrangement can be seen earlier in figure 7 A sketch of the connection to the gondola can be seen in figure 8 3 3 Thermal interfaces 3 3 1 Thermal Design 3 3 1 1 Thermal Design Requirements For different subsystems dif ferent thermal requir
64. rature at mid discharge Figure 9 LSH 20 performance 3 3 1 2 Thermal Design Description The temperature of the control box can be actively controlled by a 5 W heater Verification is done by testing Optional thermal blankets or the use of thermal paste is possible to finetune the design The temperature of the battery box will be controlled passively by ther mal insulation In addition to that self heating of batteries will be used to keep the desired temperature In order to reduce the chances of the heater getting too cold or seizing when operation begins it will be started before launch This will be thor 32 oughly tested beforehand and if it is found that this method will not operate successfully then insulation will be added as is required In order to avoid loss of seal due to changes in pipe diameters as the temperature varies steel was selected for their low coefficients of thermal expansion Flexible sealant will also be used to ensure the air tightness 3 3 2 Thermal Interfaces The experiment has conducting interfaces through the structure to the gon dola This will be the main part of power dissipation since convection is negligible in high altitudes 3 3 3 Temperatures and Thermal Control Budget 3 3 3 1 Temperature Ranges See Appendix TBD 3 3 3 2 Temperature Monitoring Temperature of the control box and at three further critical points outside the control box is continuously mea sured Critical points have to
65. re launch the following tasks need to be carried out by various team members Oct 2nd the final functional test is carried out by the whole team Oct 2nd the filters are placed in the experiment using a clean bench by Mark Fittock Oct 3rd the ground station will be setup by Martin Siegl Oct 3rd a hole will be drilled through the gondola floor by Mark Fittock Oct 3rd the military standard connector will be soldered by Martin Rudolph Oct 3rd fix outside temperature sensor with thermal paste Oct 3rd fix battery temperature sensor with thermal paste 120 min the experiment will be mounted to the gondola the electronic connections will be fixed and the experiment will be connected to the Elink by Mark Fittock and Martin Rudolph 30 min the electronic connectors are checked by Martin Rudolph 30 min the tube is opened by Mark Fittock 30 min the experiment is plugged in the microcontroller is started by Martin Rudolph 30 min the link and the temperatures are checked by Martin Siegl 0 LAUNCH 2 5 4 Post flight Analysis After the retrieval of the payload the filters will be dismounted in a clean room at either Esrange or IRF and shipped to the Institute of Experimental and Applied Physics Czech Technical University Prague Czech Republic Subsequently two techniques will be used for analysis Electron microscopy will be used for evaluation of the main structure of the aerosols The size gives useful info
66. results An overall functional test still without batteries was carried out It was con cluded that the microcontroller works and that the actuators can be moved by controlling them via the ground station The pump and the heated can be switched on and off and can be regulated via PWM The temperature sensors give feedback but the calibration appears to be incorrect Some flaws in the ground station software were detected 53 4 3 Electrical Functional Performance Test e Functional test of sensors pressure temperature with reference sen Sors e Functional and performance test of pump e Functional test of actuators e Test of interface between control system and the actuator e Test of interface between control system and the pump e Test for EMC e Full electronic system test in expected temperature and pressure ranges 4 4 Limited Life Time Elements Batteries will have a limited lifetime and also a continuous performance degradation during the flight This degradation mainly depends on tem perature and the design has to be verified during the testing phase 54 5 Ground station 5 1 Ground Control amp Electrical Ground Support Equipment The equipment that is used as EGSE Electrical Ground Support Equip ment for instrument level and system level check out testing is also used for experiment ground control during flight and will be referred to as ground station below 5 1 1 Concept The ground station is kept
67. rmation about the origin of a particle 25 volcanic cosmic or contaminate The spatial distribution of specific ele ments can be studied An image of a filter similar to the one that will be flow can be seen in figure 6 The core analysis technique is Coincidence Instrumental Neutron Activa tion Analysis CINAA 13 a technique able to detect the composition of multiple isotopes This will be carried out by the Czech Nuclear Institute us ing a neutron specific dose at Research Reactor LVR 15 for activating sample for about 100ppm strong analysis by gamma spectroscophy on site focusing on heavy metals We are expecting to find transitions between specific types of isotopes of Fe In and Co mainly These isotopes were not there previo suly as the previous calibration analysis confirmed personal corespondence results come up soon The method is very precise and can be used to detect a sub ppm fraction of elementary abundance for up to 74 elements 17 5 This technique will be used both on the filter that has been flown and on the filter that has not been flown so that the structure of the filter itself can be removed by digital post processing simple subtraction Heavier elements have larger nuclei therefore they have a larger neutron capture cross section and are more likely to be activated by fast neutrons That is of great benefit because we are mostly interested in those heavy ele ments although only present in stratosphere
68. roller The microcontroller is connected to the heating panel of the control unit and the heating clamp of the filtering unit via relays These are switched on 12 Vivo 200 250 300 350 400 Figure 2 Voltage as a function of temperature for an Epcos thermistor when the temperature drops below a certain temperature The sensor on the surface of the pump is for safety reasons It assures that the temperature of the pump is known at every time and can be switched of in case of exceeding a temperature threshold 2 3 2 2 Pressure The pressure sensor is a critical part of the electronic subsystem It determines the altitude and launches the filtering process Decision was made for the ASDXDO series by Honeywell which provides an absolute pressure range from 0 to 103 kPa This sensor is placed inside the control unit For correct operation an outgassing hole is provided 2 3 2 3 Filtering Unit The components of the filtering unit i e the valves and the pump are connected with power mosfets which can be turned on with the corresponding bits 2 3 2 4 Downlink The TTC system of the balloon is accessed via the RS232 connection of the microcontroller The crumb128 supplies a driver for that The system will be attached to a MIL C 26482 plug as stated in the BEXUS user manual 22 2 3 2 5 Heating To prevent freezing of the components through the out gassing hole heating resistors are soldered onto the PC board If the temper 13 ature i
69. s A list of abbreviations can be seen in table 10 83 BEXUS Balloon EXperiments for University Students BSPP British Standard Pipe Parallel CDR Critical Design Report or Review CINAA Coincidence Instrumental Neutron Activation Analysis COTS Commercial Off The Shelve DLR German Aerospace Centre EAR Experiment Acceptance Review ESA European Space Agency Esrange European Space Range IRF Institut for Rymdfysik Institute of Space Physics IRV Institut for Rymdvetenskap Department of Space Physics LTU Lulea Tekniska Universitet Lulea University of Technology MTR Mid Term Report NPT National Pipe Thread PCB Printed Circuit Board PDR Preliminary Design Report or Review PWM Pulse Width Modulation SNSB Swedish National Space Board SSC Swedish Space Corporation TTC Telemetry Telecommunications amp Command Table 10 Table of used acronyms 84 H Bibliography References 1 10 11 12 Tom Benson Earth atmosphere model http tinyurl com 3blc8s March 2006 Online accessed 19 January 2008 Binder steckverbinder serie 680 http www binder connector de pdfs serien 680 pdf Online accessed 21 May 2008 DE Brownlee Cosmic Dust Collection and Research Annual Review of Earth and Planetary Sciences 13 1 147 173 1985 Swedish Space Corporation Environmental conditions http www ssc s
70. s appears to have been published in 1960 by Junge et al 14 In this study an Aitken nuclei counter was used with a pressurised chamber to determine the concentration size distribution and chemical composition of stratospheric aerosols A detailed description can be found in the cited paper The particle concentration at an altitude of 20 to 30km was measured to be less than 1 particle per cubic centimetre for particles smaller and larger than 12 0 l1um in radius with limited quantitative results on the size distribution though particles smaller than 0 01um were found to have short lifetimes and particles larger than 1 04m were found to be rare Most particles were between 0 1um and 1 0um Chemical analysis showed a large amount of sulphur particularly for particles between 0 1um and 1 04m in diameter A small amount of silicon and iron was also detected Elterman et al used ground based optical measurements to determine features on tropospheric and stratospheric dust 6 A comprehensive study was published in 1975 by Rosen Hofmann and others focusing on the global 24 and seasonal 10 dependence as well as size distribution 23 and sources 9 of dust concentrations using a large number of balloon measurements and a dedicated detector described in 10 for particles with a diameter gt 0 3um Measurements above Bar row Alaska United States 71 N in November 1973 show a mixing ratio of around 6particles mg air at an alt
71. ss of a sensor or communication with a sensor Loss of the tempera ture sensor in the control box can be fatal for the microcontroller Loss of the temperature sensor on the pump can be fatal for the pump Loss of pressure sensor in conjunction with loss of ground communication Autonomous mode can lead to a delayed experiment start 3 1 1 3 Structure In order to avoid failure propagation for the struc tural components most components are bracketed to a frame structure that connects to the strong and rigid exterior frame In the case that a component does manage to break away from another they should remain fixed to the other components Of concern are the large mass components such as the pump and actuators Particular care has been taken to ensure that they are secured and redundant beams have been used Although the pump used is small and not running at a high frequency failure propagation is still a concern Although the experiment should with stand catastrophic failure of the pump if it is of concern for other experi ments further measures can be taken to protect from projectiles that may occur during malfunction 3 1 1 3 1 Single point failures Due to the limited scope of this project multiple redundancies were not possible for many of the compo nents The high cost of the pump and actuators means that only one pipe system could be used Unfortunately this results in multiple single point failure possibilities In order to lower t
72. standards All moving parts are either completely or practically sealed off no specific in structions regarding safety are needed for this 3 1 3 Materials Because of the nature of this experiment a number of different metals were selected depending upon the applications Although aluminium is preferred for many uses it is not suitable for others 3 1 3 1 Aluminium The frame and structure of the experiment are con structed from prefabricated beam materials Although aluminium is both light and easily worked there are difficulties with such a balloon flight and the temperatures that will be experienced Due to the high coefficient of thermal expansion aluminium was deemed inappropriate for the piping due to leakage concern 3 1 3 2 Brass Brass fittings were selected over the more standard steel fittings due to the reduction in cost Brass retains the low friction and low coefficient of using steel whilst being cheaper The reduced durability of the fittings is not a concern because of the low operating period of the equipment 3 1 3 3 Steel It was decided that for the piping steel would be used The low coefficient of expansion was the deciding factor for using the steel and since the amount of piping required is not large and the diameter small the mass payoff was deemed acceptable 29 3 1 4 Declared Components List A full components list can be found in appendix E 3 2 Mechanical interfaces Figure 7 shows the simple b
73. t is designed to collect aerosols in the stratosphere and do a post recovery analysis The experiment consists of a pump sucking air through a filter that is able to catch particles down to 0 3um It will fly on a stratospheric balloon launched from Esrange by Eurolaunch in October 2008 as part of the BEXUS 7 campaign A system of tubes and valves will ensure that no air flows through the filter before or after the balloon reaches floating altitude Upon recovery the filters will be collected and analysed using electron microscopy and neutron activation analysis Contents 1 Introduction 9 bd FO sos Silent O Y IAS AER eei wu 9 1 2 Acknowledgements and sponsors 10 2 Experiment description 11 2 1 Scientific Objectives gato g vus d eu ed De do ede 11 22 Experiment summary 4x 9192 A dus 11 200 Hardware v aana dei qr kald er Galde te nd 12 2 3 1 Components cl ic uli ol k te dn 12 de a o Py bes doe ed ae deem Qi dd sved ke 12 2 3 2 1 Temperature iE pk 12 DDI PRESS En A uer dit dy deu SE ee Oh IE ayaz 13 2023 Filtering A An a DR 13 20 02 Downlink kh o Ae efie a bi e 13 2325 A sis oan ute xo ch maru say 13 2 3 2 6 Risk analysis tne D Dora 2 eid 14 ea soe Frere feka Be de uos 14 2 3 3 1 Pipe substructure es 14 2 3 3 2 Manufacturing techniques paa 16 2 3 3 3 Volume budget uite teu RO a psi 16 2 3 3 4 Frame Stress Analysis 17
74. ta for zz 30 min The data packet looks as follows Byte 112131451 67 9 10 11 12 Content P D ID time temp 1 temp 2 39 12 13 14 15 pressure CRC checksum r The first byte indicates the start of the packet the second byte iden tifies the sender P probe the third byte describes the content D data A two type ID assures the correct identification of every packet The status packet is similar S status Byte 1112131451 67 8 9 10 Content P S ID time pump heater 11 12 13 14 15 valves mode CRC checksum r Command packets are kept shorter to reduce the risk of corruption during transmission Byte LI 2 3 8 9 10 Content G command CRC checksum r The first byte indicates the start of the packet the second byte iden tifies the sender G ground bytes 3 9 are for the command itself and the checksum 3 7 5 Telecommand Definitions The possible commands are e 0K to signal a working connection every 10 s e HELO to check the uplink handshake e OV ID to open the valve with ID e CV ID to close the valve with ID e HEON ID to switch on the heater with ID PUMP 1 byte
75. those It is currently being built by an international team of students E mail located mainly in Kiruna Sweden It is set to be launched from Esrange October 2008 The Earth s stratosphere contains aerosols of various origins including aerosols of volcanic and cosmic origin An experiment is designed to collect aerosols in the stratosphere and do a post recovery analysis The experiment consists of a pump sucking air through a filter that is able to catch particles down to 0 3 um It will fly on a stratospheric balloon launched from Esrange by Eurolaunch in October 2008 as part of the BEXUS 7 campaign A system of tubes and valves will ensure that no air flows through the filter before or after the balloon reaches floating altitude Upon recovery the filters will be collected and analysed using electron microscopy and neutron activation analysis The scientific background and the experiments objectives are briefly described on the background page The experiment page describes the experiment itself A detailed description of both can be found in the Critical Design Review PDF 2 6 MB last updated on the 2nd of June 2008 When available results will be posted on the results page Finally a description of the team and a word for our sponsors is available Stratospheric Census would like to thank the following sponsors for making this project possible Figure 20 A screenshot of the front page of the website Additionally the team would of c
76. tific background work and coordinating the documentation e Martin Rudolph from Germany Martin s field of work is the electronic circuit design and the power budget e Martin Siegl from Austria Martin has worked on the presentation for ESA sponsorship allocating project management pump information various small tasks and will do microcontroller programming e Jaroslav Urbaf from the Czech Republic Besides developing the idea of Stratospheric Census he did research on possible filters As a team comprised of five different nationalities from ESA member countries an ESA associated country and a non ESA country we are proud to reflect the European spirit of ESA in a global cooperation within our group 6 2 Relation with various organisations IRV The project has been registered as a course with the Department of Space Physics IRV part of Lule University of Technology LTU based in Kiruna Sweden The course supervisors are Kjell Lundin and 58 Alf Wikstrom If the supervisors deem the work of sufficient quality the group members will get 15 0 ECTS credits for the course work Progress reports are sent to the IRV supervisors twice a month IRV is also one of the funding organisations providing 5000 Swedish Crowns for parts primarily electronic components to be ordered via the institute SSC Esrange The balloon will be launched from Esrange the launch fa cility in Kiruna Sweden operated by the Swedish Space
77. val upon atmospheric entry and the duration in the stratosphere Particles that are big enough to survive the atmospheric heating are known as meteorites fall straight through the stratosphere down to Earth and are many orders of magnitude larger than what we are studying The chance of collecting a meteorite is rather small Particles that are small enough to circularise their orbits and then survive heating and mechanical stress while descending to around 40 km altitude are smaller than 100jm 3 As this survival is biased collection of strato spheric dust does not give representative information to the distribution and composition of interplanetary dust The flux of 10um particles is around 1m day and their density is around 3 107 m Particles smaller than 2um are hard to detect as such because the total mass is much smaller than the total mass of submicron sulfate aerosols However the elements are quite different from those of volcanic origin and are thus quite possible to detect if any particles have been collected at all such as iron nickel calcium aluminium titanium magnesium 3 The composition and form of those depends on the size of the particles and the exact likelihood to encounter those varies The identification as extraterrestrial is usually done based on this information which is not available when analysing with neutron activation analysis D 3 Location specific considerations D 3 1 Geography and climate
78. ves filters etc while the PCB board and the mechanical structure 2 3 3 are produced by the team itself 11 2 3 Hardware 2 3 1 Components A complete list of components with references to the relevant data sheets can be found the table in appendix E 2 3 2 Electronics Temperature pump Valve 1 Temperature control chamber 5 Pump Pressure control chamber Heater control chamber Pressure optional Temperatur 2 optional Temperatur 3 optional Figure 1 Schema for the information flow The heart of the electronics control system forms an ATMEGA128 micro controller on a Crumb128 board It senses pressure and temperature from various points and makes decisions when to switch on the filtering unit A logical schema can be seen in figure 1 a circuit diagram is in figure 17 on page 64 in appendix A 1 2 3 2 1 Temperature The temperature is measured inside the control system at one point on the surface of the pump and optional two additional points This is done by means of a voltage divider formed by a thermistor and a 30k resistor The resistance of the thermistor is calculated by the B parameter equation R 4 For the Epcos thermistor 8 B 3970 at To 300K In combination with the resistance it yields the following voltage vs temperature curve The voltage is fed into an analog input of the microcont
79. xperiment and caught by the filter immediately Those are particles that we are not interested in and are outside the scope of our experiment they are thus considered to be contamination There may also be ice particles that are neither anthropogenic nor aerosols though those are rare in the very dry stratosphere Since the team will fly a man made experiment contamination is an issue as well Apart from the common composition of materials from which the experiment structure is built there exists a local deviation from the stan dard Earth isotope ratio conditions The balloon launch platform contains material from the regional iron ore mining thus introducing a magnetite contamination Fine grains may stick to the aluminium gondola and detach later during the flight possibly entering the experiment The iron ore from Kiruna has slightly specific ratio s of nuclide compositions 42 It is safe to assume that all surfaces and materials in the balloon gondola system will outgas Outgassing can result from desorption diffusion and decomposition 25 The amount of mass loss due to diffusion is given by dm e R AE SIUE 2 In equation 2 qo is a reaction constant to be determined experimentally E is the activation energy typically between 5 and 15 Kcal Ris the universal gas constant T is the temperature and t is the time This equation was derived for a vacuum The stratosphere is no vacuum but the atmospheric density is cons
80. y Due to concerns about opening those valves in the stratosphere the team decided to use valves that are actuated only electrically The team is aware that a power failure can lead to these valves not closing For vacuum test of valves for thermal tests and for tests of the PCB the testing section 4 2 was updated Experiment Acceptance Review 2008 09 19 2008 09 22 4 0 4 1 Updated mass budget pin allocations schematics and website and removed refer ences to abandoned or changed plans More details on pre flight procedure wrote on test results Table 6 Table of revisions 70 C Outreach Programme As part of Stratospheric Census we are aware of the importance of reach ing out to the public educating them about the work carried out by the team We have therefore gotten in contact with Hakan Sjunnesson writer for among others the Swedish popular science magazine Ny Teknik New Technology In an initial interview we already explained the project to him and he is going to follow the progress closely In September 2008 a website was established following up on a blog at http www stratospheric census org A screenshot of the website can be seen in figure 20 Stratospheric Census Team 1 Stratospheric Census is a student project to collect aerosols dust in the stratosphere by flying a filter on a balloon and Sponsors to subsequently perform an on ground analysis on
81. y danger due to voltages of maximum 12V As mentioned before the MIL STD connector will be borrowed from Es range for the time of ight 3 5 4 Connector Pin Allocation See appendix A 3 for a full table with pin allocations and configurations 3 6 OBDH Interface Requirements 3 6 1 E Link connection An RS 232 connection to the E Link unit is required It will be used at 9600 bps with one packet comprising 1 start 8 data 1 stop bit No flow 35 control 3 6 2 Channel Allocation Interface Main Telemetry amp Monitor Downlink 1 Telecommand Uplink 1 Table 2 Experiment OBDH Interface Channels In the E Link connection these channels are shared with other experimenters 3 6 3 Bit Rate Requirements Stratospheric Census does not continuously transmit data Data packets are sent every 10 s status packets upon request and or status change The operational scenarios as outlined in the software descriptions are Normal Mode and Autonomous Mode For these the bit rate requirements are Worst case Minimum Autonomous Mode 0 bit s e Normal Normal Mode In a 10s interval it has to be possible to transfer one data packet and if need arises one status packet down link A safe lower limit therefore are 50 bit s If in Normal Mode this bit rate cannot be sustained the buffer of the E Link unit would slowly be filled up by the Stratospheric Census microcon troller 3 6

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