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1. 100 85GHz V pol Ts Kelvin Integer 2 cel_85h 128 3600 0 01 100 85GHz H pol Ts Kelvin Arrays 1 dimension is lo res cell number 2 dimension is max number of lo res scans Type Name Scale Offset Description Integer 2 cel_19v 64 1800 0 01 100 19GHz V pol Ts Kelvin Integer 2 cel_19h 64 1800 0 01 100 19GHz H pol Ts Kelvin Integer 2 cel_22v 64 1800 0 01 100 22GHz V pol Ts Kelvin see Note 5 Integer 2 cel_37v 64 1800 0 01 100 37GHz V pol Ts Kelvin Integer 2 cel_37h 64 1800 0 01 100 37GHz H pol Ts Kelvin RSS Tech Memo 052212 May 22 2012 Note 1 Alpha numeric time Astart_time is a 24 byte character string formatted as follows READ astart_time 14 13 3 412 2 F9 6 LYEAR IDAYJL IMON IDAYMO IHOUR IMINUTE SECOND LYEAR year 1987 2003 IDAYJL Julian day 1 366 IMON month 1 12 IDAYMO day of month 1 31 IHOUR hour of day 0 23 IMINUTE minute of hour 0 59 SECOND second of minute 0 59 999999 Note 2 Quality Control Bits Iqual_flag indicates the quality of the scan If it is not zero then there is a problem with the scan and we advise Users to look at the individual bits to decide if the scan should be used In general if iqual_flag is not zero the scan should be skipped However there are situations where simply filtering on iqual_flag not equal zero will discard too much data For example for the F08 SSM I the 85 GHz channels for the most part are erroneous and bits 9 10 and2. Sun Glint The sun glint angle is defined as the angle between two vectors a and b Vector a is the vector going from the SSM I footprint to the SSM I antenna Vector b is the vector pointing in the direction of sunlight reflected off the Earth surface at the location of the SSM I footprint assuming that the earth surface is a specular reflector Low sun glitter angles mean that reflected sunlight is being received by the SSM I Note 4 Land and Sea Ice Percentage land contamination is defined as the percentage of the power received by the SSM I 19 GHz antenna pattern that comes from land The sea ice flag is based on a monthly climatology A value of cel_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 cel_ice 0 RSS Tech Memo 052212 May 22 2012 Note 5 22 GHz Brightness Temperature The SSM I sensor is not dual polarization at 22 235 GHz Hence the conversion from antenna temperature to brightness temperature needs to be done differently This problem is discussed on page 13 of the User s Manual SSM I Antenna Temperature Tapes Rev 1 For V7 we use the following to22v 1 01911 ta22v 1 93574 for earth incidence angle of 52 7 to22v 1 01865 ta22v 2 05980 for earth incidence a
3. 12 will usually be set For this case if the User does not need 85 GHz observations then bits 9 10 and 12 should be ignored The acronym oob denote out of bounds Bit 0 Scan is missing there are no data Missing scans that occur in the middle of an orbit are included in the orbital file as zero filled spacers However missing scans that occur at the beginning or end of the orbit are not included Scan_time is set to 1 e30 Bit 1 Scan occurs during a period of erroneous data This problem only occurs for the early SSM I data F08 F10 F11 and F13 before 1999 See SSM I Ta User s Manual Revision 2 December 1993 Bit 2 Scan affected by calibration errors due to NRL scan averaging This problem only occurs for the early SSM I data between October 9 1990 and August 29 1992 See SSM I T User s Manual Revision 2 December 1993 Bit 3 Thermistor readings for scan are out of bounds Bits 4 10 These indicate a problem with the calibration data for the scan These 7 bits refer to channels 19V 19H 22V 37V 37H 85V and 85H respectively The following types of anomalies will trigger this flag a Cold calibration counts and or hot calibration counts are out of bounds b Automatic gain control setting is currently changing Bit 11 Removal of moon contamination in cold mirror not possible for lower frequency channels 19 37 GHz Bit 12 Removal of moon contamination in cold mirror not possible for 85 GHz channels Note 3
4. RSS Tech Memo 052212 May 22 2012 USER S MANUAL SSM I Brightness Temperature Version 7 1 INTRODUCTION This document describes the Version 7 V7 SSM I Brightness Temperature Tg Dataset produced by Remote Sensing Systems RSS This document should be read in conjunction with the earlier versions of RSS SSM I Users Manuals which give more details on the SSM I data including o Users Manual SSM I Antenna Temperature Tapes Rev 1 December 1991 o Users Manual SSM I Antenna Temperature Tapes Rev 2 December 1993 o SSMI Version 6 Calibration doc October 24 2010 These documents are available from Remote Sensing Systems This current document is primarily intended to describe the format and content of the V7 TB dataset The V7 Tg dataset incorporates improved geolocation calibration and quality control procedures in a consistent manner for the entire 25 year SSM I dataset In addition the six SSM Is F08 F10 F11 F13 F14 and F15 have been carefully inter calibrated among themselves and with WindSat AMSR E and the F17 SSMIS This allows investigators to confidently use these SSM I products for detailed interannual and decadal trend studies We are in the process of writing a V7 Calibration Report that will describe the improvements in geolocation and calibration 2 DATA FORMAT The SSM I data are stored in orbital files The file names have the form _r dat see note at end of document where is the SSM I sa
5. ngle of 53 7 These two incidence angles bracket the incidence angle variation experienced the SSM Is For incidence angles between 52 7 and 53 7 a linear interpolation is used to find tb22v Note that the array corresponding to tb22v is called cel_22v 4 Zero Tg Values A Tg value of zero indicates no Tz value is available to the User Zero Tg values occur when then the following events occur a If bits 0 1 2 and or 3 in the scan quality flag are set then all Tgs in the scan for all channels are set to zero b If either the v pol or h pol calibration problem bit is set for a particular frequency then all Tgs in the scan for that frequency both v pol and h pol are set to zero c If the Earth viewing count is out of bounds or if the recovered Earth viewing count is not an integer then the Tsg just for that observation is set to zero The User must check if Tp 0 and exclude these missing values 5 Advice on Quality Filtering For a given observation cell look at the Tg values required for your particular applications If any of these is zero skip the cell Also if your application requires the low frequency channels 19 37 GHz and bit 11 is set skip the cell Likewise if your application requires the high frequency channels 85 GHz and bit 12 is set skip the cell 6 Reading Variables The orbital files are simple binary files Each file is exactly 9 561 636 bytes because a fixed number of scans 3600 is always
6. number Integer 4 numscan 1 0 Number of hi res scans Character 24 astart_time n a n a Date and time for first scan in file see Note 1 Vectors Dimension is max number of hi res scans Type Name Scale Offset Description Real 8 scan_time 3600 1 0 Scan time seconds from begin of January 1 2000 0Z Real 8 orbit 3600 1 O Orbit position eg 9999 95 Real 4 sc_lat 3600 1 0 Spacecraft nadir geodetic latitude at time scan_time deg Real 4 sc_lon 3600 1 0 Spacecraft nadir east longitude at time scan_time deg Real 4 sc_alt 3600 1 0 Spacecraft nadir altitude at time scan_time meters Integer 4 iqual_flag 3600 1 0 scan quality flag see Note 2 Arrays 1 dimension is hi res cell number 2 dimension is max number of hi res scans Type Name Scale Offset Description Integer 2 cel_lat 128 3600 0 01 0 observation geodetic latitude deg Integer 2 cel_lon 128 3600 0 01 180 observation east longitude deg Integer 2 cel_eia 128 3600 0 002 45 observation earth incidence angle deg Integer 2 cel_azm 128 3600 0 01 180 observation earth azimuth angle clockwise from North deg Integer 2 cel_sun 128 3600 0 01 O observation sun glint angle deg see Note 3 Integer 2 cel_Ind 128 3600 0 4 O observation land percentage see Note 4 Integer 2 cel_ice 128 3600 1 0 observation sea ice flag see Note 4 Integer 2 cel_85v 128 3600 0 01
7. tellite number i e 08 10 11 13 14 or 15 and is the orbit number i e 00001 to 99999 By definition an SSM I orbit begins near the South Pole at the point where the z component i e north south of the spacecraft velocity vector changes from a negative value to a positive value Note that this is a different convention than used in previous versions For example for the V6 SSM I dataset orbits began at the spacecraft ascending equatorial node This change in convention of V7 brings uniformity to SSM I SSMIS WindSat and AMSR E Each orbital file contains additional scans at the beginning and end of each orbit For example the file for orbit 10000 contains scans starting with orbit position 9999 95 and ending with orbit position 10001 05 The data at the end of orbit file 10000 are then given again in orbit file 10001 This 5 overlap of the orbit files facilitates user requirements that involve scan averaging In order to reduce the downlink telemetry data rate the SSM I only takes measurements for the 3 lower frequencies 19 22 and 37 GHz every other scan The 85 GHz measurements are taken every scan Likewise the lower frequency measurements are only taken at every other along scan position The 85 GHz measurements are taken at all scan positions For example an orbital file typically has about 3546 scans and the total number of observations taken during the Earth viewing portion of the scan is 128 Thus the arrays of 85 GH
8. used for the arrays For example if there are 3546 actual scans for the orbit then bit O of the quality flag is set for scans 3547 3600 Also the scan time is set to 1 e30 for these scans at the end When reading the file contents the order of the variables is the same as that shown in the table in Section 3 7 Copyright Notice This Version 7 SSM I Brightness Temperature Dataset is the intellectual property of Remote Sensing Systems All rights are reserved Copyright 2012 Remote Sensing Systems Internal backup copies within your organization are permitted Please contact Remote Sensing Systems if you have further copying requirements Organizations wanting this dataset should directly contact Remote Sensing Systems It is our intention to freely provide this dataset to the research community notwithstanding the marginal cost of reproduction and delivery note file name as originally listed in this document dated May 22 2012 was incorrect The file name format has been changed in this document March 2014 by D Smith
9. z observations are 128 by 3546 However the arrays for the lower frequency observations are 64 by 1773 The 85 GHz grid is called hi res and the lower frequency grid is called lo res In the V7 Tz orbital files all parameters are given on the hi res grid except for the lower frequency brightness temperatures which are given on the lo res grid In order to associate a hi res value i e latitude and longitude with a lo res Tg the following mapping is used Let ice _lo iscn_lo denote the indices for a lo res Tg The indices for the corresponding hi res value are icel_hi 2 icel_lo 1 iscn_hi 2 iscn_lo 1 In other words the lo res grid corresponds to the odd numbered elements in the hi res grid In this way the User can assign a latitude longitude incidence angle etc to the lo res Tegs The maximum number of scans in an orbital file is about 3546 To be safe we allow for a maximum value of 3600 The vectors and arrays in the data file are a fixed dimensional size with 3600 being the scan dimension 3 Description of Variables RSS Tech Memo 052212 Each file contains the following scalars vectors and arrays Scaling and offsets are applied as follows Actual_Value in units given Scale Stored_value Offset May 22 2012 Scalars Type Name Scale Offset Description Integer 4 ksat 1 O Satellite number 08 10 11 13 14 or 15 Integer 4 iorbit 1 O Integer orbit
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