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1. is the following where the stated condition is true if the bit is turned on oob out of bounds Bit not used Bit scan is missing or no time for scan is available scan time is set to 0 Bit time for ephemeris data is oob Bit thermistor mux index oob Bit insufficient information to compute spacecraft position Bit ephemeris time more that 90 sec from scan time Bit ephemeris times are not bracketing scan time Bit ephemeris times are too close in time Bit inconsistent ephemeris times vs location hot load thermistor values are oob 0 1 2 3 4 Bit 5 location for ephemeris is oob 6 7 8 9 0 6 The Ts quality flags ICAL FLAG and ICAL FLAG HI indicate the quality of the Ts for the lower channels and higher channels respectively If it is not zero then there is a problem and we advise Users in general not to use the set of Ts The definition of the bits for the Ts quality flags is the following where the stated condition is true if the bit is turned on Bit 0 scan position index out of sync so far as never happened Bit 1 reverse engineered counts not integer extremely rare Bit 2 anomalous jump in counts Bit 3 removal of moon contamination in cold mirror not possible hes Other problems can affect the quality of the TB These include oob calibration counts and or oob Earth counts If any of these conditions occur including the conditions in item 6 above the Ts value is set to zero THE USER MUST CHECK IF TB 0 AN2. D EXCLUDE THESE MISSING VALUES 5 Near Realtime Data Files In addition to the orbital files RSS also offers near realtime data files These files correspond to a single telemetry dump from the spacecraft to a ground station As such these files do not correspond to any particular orbit They may be very small an orbit segment or very large multiple orbits The format for these realtime files is identical to the orbital files The only thing that is different is the file naming convention and the length of the files which varies with each file The files are named according to the time of the first scan in the file using the following convention write filename 9001 ksat lyear imon idaymo ihour iminute isecond suffix 9001 format rss_tb_f i2 2 y i4 4 m i2 2 d i2 2 h i2 2 m i2 2 s i2 2 al dat 66 99 where suffix is a single character usually a If there are multiple downlinks having the same start time then the suffix will be b for the second one and so on 7 Copyright Notice The SSM IS Brightness Temperature Dataset is the intellectual property of Remote Sensing Systems All rights are reserved Copyright 2010 Remote Sensing Systems Internal backup copies within your organization are permitted Please contact Remote Sensing Systems if you have further copying requirements
3. RSS Tech Memo 061010 June 10 2010 USER S MANUAL SSM IS V7 BRIGHTNESS TEMPERATURES 1 Introduction This document describes the format and reading procedure for the SSM IS V7 Brightness Temperature Tg Dataset produced by Remote Sensing Systems RSS This dataset is a fully calibrated accurately geolocated time series of Earth brightness temperatures The SSM IS temperature data records are first reverse engineered back to the raw telemetry data which is the starting point for our data processing We process the raw counts to Tg using a standard set of proven algorithms This data handling process is the same that we use for all microwave imagers including SSM I TMI AMSR and WindSat In this way we maintain consistency among the various sensors and platforms The SSM IS dataset described herein is a subset of the complete SSMAIS channel set It includes the following 7 channels 19 35V 19 35H 22 235V 37V 37H 91 7V and 91 7H Two sets of geolocation parameters are provided one for the lower channels 19 37 GHz and the other for the 91 7 GHz channels Each 1 9 second scan contains 90 lower channel observations and 180 91 7 GHz observations The odd numbered 91 7 GHz observations are in close proximity to the lower channel observation locations but there is some difference so we provide locations for both types of observations Note that the locations of the 19 and 22 GHz observations are slightly different from those of the 37 GHz obse
4. an 1 2000 02 ORBIT real 8 Orbit position SCLAT real 4 Spacecraft geodetic latitude at time ATIME deg SCLON real 4 Spacecraft east longitude at time ATIME deg SCALT real 4 Spacecraft altitude at time ATIME km SCN_FLAG integer 4 Scan quality flag see below CAL FLAG integer 4 Ts quality flag 19 37 GHz see below CAL FLAG HI integer 4 Ts quality flag 92 GHz see below Arrays that depend of the 90 scan positions for the lower channels 19 37 GHz LAT 90 real 4 Geodetic latitude of footprint deg LON 90 real 4 Fast longitude of footprints deg EIA 90 real 4 Earth incidence angle for footprint deg EAZ 90 real 4 Earth azimuth angle for footprint deg SUN 90 real 4 Sun glitter angle for footprint deg LND 90 integer 4 Land flag O open ocean 1l near coast 2 land 0 1 2 CE 90 integer 4 Sea ice flag O very unlikely 1l possible 0 1 TB 5 90 real 4 Brightness temperatures 19V 19H 22V 37V 37H Kelvin Arrays that depend of the 180 scan positions for the higher channels 92 GHz LAT HI 180 real 4 Geodetic latitude of footprint deg LON HI 180 real 4 Fast longitude of footprint deg EIA HI 180 real 4 Earth incidence angle for footprint deg EAZ HI 180 real 4 Earth azimuth angle for footprint deg SUN_HI 180 real 4 Sun glitter angle for footprint deg LND HI 180 integer 4 Land flag O open ocean 1l near coast 2 land 0 1 2 CE_HI 180 i
5. ent set of sensor calibration methods radiative transfer model and geophysical retrieval algorithms It is our intention to provide Users with a complete set of Version 7 products for all sensors in the near future probably near the end of 2010 In the meantime for SSM IS instruments we are providing the Users with software for converting the V7 brightness temperatures to the V6 calibration reference The conversion to V6 is done by setting the input argument iver to see Section 3 The V7 to V6 conversion is quite simple Tzs 4o ayTpry OyT 57 y 1 where subscripts V and H refer to v pol and h pol and subscripts 6 and 7 denote version number Each channel has its own set of a coefficients It should be noted that the retrograde V6 brightness temperatures still have all of the V7 adjustments listed above The only difference is that the absolute calibration has been adjusted to match our V6 calibration So until Version 7 data become available for all sensors Users can use the Version 6 retrograde product to maintain consistency with their previous research that was based on the Version 6 SSM I Tg 3 Data Format for Complete Orbital Files The SSM IS data are stored in orbital files The file names have the form _rittHt t dat where is the SSM JIS satellite number i e 16 17 and is the orbit number i e 10000 By definition an SSM IS orbit begins at the spacecraft southern most latitude near the South P
6. g this routine the L1b file must be opened by the user The argument iver is the version option Setting iver 0 will provide V7 Tg setting it to 1 will provide V6 Tg The subroutine does all the necessary conversions and stores the data in the common L1B_DATA The next section describes the content of this common 5 Description of Variables The first two variables in the common L1B_DATA come from the header record and are KSAT integer 4 satellite number 16 17 NUMSCAN _integer 4 number of scans in the file The remaining variables come from the scan records which are all arrays with the last dimension corresponding to the scan number We have set this last dimension to maxscan 10000 which is much larger than needed for a single orbit file The maximum number of scans in a single orbit file is about 3800 However we use a value of 10000 because the real time data files can sometimes be this large The User can set maxscan 3800 if only processing orbital files not real time files The scan records consist mostly of integer 2 values which are scaled by the read routine into the common data listed in the following table Description of Common L1B DATA NOTE Notation for the scan number dimension last index is suppressed Arrays that do not depend on scan position ATIME char 24 Time for the begin of the scan see below for alpha numeric format ITIME 2000 integer 4 Time for the begin of the scan integer seconds for J
7. nteger 4 Sea ice flag O very unlikely 1l possible 0 1 TB_HI 2 180 real 4 Brightness temperatures 92V 92H Kelvin Notes The time ATIME is a 24 byte character string formatted as follows READ ATIME 14 13 3 412 2 F9 6 LYEAR IDAYJL IMON IDAYMO IHOUR IMINUTE SECOND LYEAR year 1987 2050 DAYJL Julian day 1 366 MON month 1 12 DAYMO day of month 1 31 HOUR hour of day 0 23 MINUTE minute of hour 0 59 SECOND second of minute 0 59 999999 2 The earth azimuth angle is measured clockwise from North 3 The sun glitter angle is defined as the angle between two vectors a and b Vector a is the vector going from the earth footprint to the sensor antenna Vector b is the vector pointing in the direction of sunlight specularly reflected off the Earth surface at the footprint Low sun glitter angles mean that reflected sunlight is being received by the sensor 4 The sea ice flag is based on a monthly climatology A value of ice 0 means that we have never seen sea ice at that location and month since the first SSM I was launched in 1987 Hence it is extremely unlikely that the footprint will contain ice The one exception to this is icebergs particularly off the East Coast of Argentina which sometimes pass through areas of ice 0 5 The flag ISCN_FLAG indicates the quality of the scan If it is not zero then there is a problem and we advise Users in general to skip the scan The definition of the bits in ISCN_ FLAG
8. ole Note that this convention is different than that used for Version 6 SSM I which had the orbit numbering starting at the ascending equatorial node Each orbit file contains 5 redundant data at both the beginning and end of each orbit For example the file for orbit 10 000 contains scans starting with orbit position 9 999 95 and ending with orbit position 10 001 05 The data at the end of orbit file 10 000 are then given again in orbit file 10 001 This 5 overlap of the orbit files facilitates User requirements that involve scan averaging Each file contains a header record that gives the satellite number and the number of scans in the file The scan records then follow All records are in simple binary format with no record marks The file should be opened as a binary unformatted file depending on compiler A typical file will contain the header record plus a maximum of about 3800 scan records and hence the total file size should be around 17 000 Kb All data words within a file are signed integers except for the scan time which is a 24 byte character sting The data files were generated on an Intel PC based system and hence have little endian convention in which the least significant byte is stored first in the integer 4 Subroutine read _l1b_file f The subroutine read_lb_file f is a Fortran tool for reading the data files It has two input arguments ilu and iver The argument ilu is the logical unit number of the L1b file Before callin
9. rvations Fortunately the footprints of the 19 and 22 GHz observations have sufficient overlap so that optimum interpolation can be used to move the 19 and 22 GHz footprints to the location of the 37 GHz footprints thereby avoiding the need to have a third set of geolocation parameters The adjustment of the locations via optimum interpolation is highly accurate and should be of no concern to most if not all users A number of adjustments and corrections are applied to the data to achieve full calibration These include 1 Adjustments applied to the SSM IS pointing angles to achieve proper geolocation 2 Corrections applied to remove the effects of the SSM IS emissive antenna The emissive antenna affects all SSM IS channels Corrections applied to remove the Moon intrusion into the cold mirror Corrections applied to remove the Sun intrusion into the hot load Flagging of anomalous jumps in the radiometer counts Application of extensive quality control with respect to geolocation information and radiometer performance 7 Adjustments to the antenna pattern coefficients to provide precise 0 1K or better inter calibration with all other microwave imagers DN ON aS 2 Converting Version 7 to the Version 6 Calibration Reference RSS has recently transitioned to this new Version 7 processing for both brightness temperatures and geophysical products with regards to in house data processing The Version 7 products benefit from a completely consist
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