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TRMM Microwave Imager (TMI) LEVEL 1B Calibrated Brightness Temperature (TB) Product

Data Access:

1B11: http://disc.sci.gsfc.nasa.gov/data/datapool/TRMM_DP/01_Data_Products/01_Orbital/02_Tmi_Brtemp_1B_11/
Contents:

Summary

This document provides basic information on 1B11, the TRMM Microwave Imager (TMI) LEVEL 1B calibrated Brightness Temperature (TB) data product. The TMI calibration algorithm (1B11) converts the radiometer counts to antenna temperatures by applying a linear relationship of the form Ta = c1 + c2 x count. The coefficients are provided by the instrument contractor. Antenna temperatures are corrected for cross-polarization and spill over to produce brightness temperatures (Tb), but no antenna beam pattern correction or sample to pixel averaging are performed. Temperatures are provided at 104 scan positions for the low frequency channels and 208 scan positions at 85 GHz. There are four samples per pixel (3 -dB beamwidth) at 10 GHz, two samples at 19, 22, and 37 GHz, and one sample per pixel for the 85 GHz.

Data Flow Description

TMI Level 1A ==> TMI Calibrated Brightness temperature (1B11)

The data flow of all products are shown in the Satellite Algorithm Flow Diagram.

Data Set Description

Data Characteristics

TRMM 1B11 (TMI) Data Characteristics
  Pre-boost (before 2001-08-07) Post-boost (after 2001-08-24)
Temporal Coverage Start Date: 1997-12-08
Stop Date: 2001-08-07		 Start Date: 2001-08-24
Stop Date: -
Geographic Coverage Latitude: 38°S - 38°N
Longitude:180°W - 180°E		 Latitude: 38°S - 38°N
Longitude:180°W - 180°E
Temporal Resolution About 91.5 minutes per orbit
About 16 orbits per day
More information about revisit frequency		 About 92.5 minutes per orbit
About 16 orbits per day
More information about revisit frequency
Spatial Resolution 4.4 km at 85.5 GHz 5.1 km at 85.5 GHz
Scan Characteristics Swath Width: 760 km
Pixels/Scan: 104 (low resolution)
                    208 (high resolution)
Scans/Second (SS): 36.100/60
Seconds/Orbit (SO): 5490
Average Scans/Orbit: nscan = SS*SO+100 = 2991		 Swath Width: 878 km
Pixels/Scan: 104 (low resolution)
                    208 (high resolution)
Scans/Second (SS): 36.100/60
Seconds/Orbit (SO): 5550
Average Scans/Orbit: nscan = SS*SO+100 = 3023
Average File Size Compressed: ~14.4 MB
Original: ~14.4 MB		 Compressed: ~14.7 MB
Original: ~14.7 MB
File Type HDF HDF

Data Format Structure

Further information on the contents and structure of the TMI rain profile (2A-12) product can be found in Volume 3 of the "File Specifications for TSDIS Products - Level 1" .

Data Format Structure for 1B11, TMI Brightness Temperature
Name Type Record
Size
(byte)		 Dim Size/
# of Records		 Scaled
by		 Range Unit Description
ECS Core Metadata Char Attribute 10,000  - - - - ECS Core Metadata.
PS Metadata Char Attribute 10,000  - - - - Product Specific Metadata.
Swath Structure Char Attribute 5,000  - - - - Specification of the swath geometry.
Scan Time Vdata Table 9  nscan - - - Time associated with each scan.
Geolocation Float SDS 4  2*208*nscan - - degree Earth location of the center of the IFOV at the altitude of the earth ellipsoid. The first dimension is latitude and longitude, in that order. The next dimensions are numbers of pixels and scans.
Scan Status Vdata Table 21  nscan - - - Status of each scan.
Navigation Vdata Table 88  nscan - - - Spacecraft geocentric information.
Calibration Vdata Table 95  nscan - - - Calibration.
Calibration Counts Integer SDS 2  16*2*9*nscan - - - Calibration measurement, in counts. Dimensions are: samples, load, channel, and nscan.
Satellite
Local Zenith Angle		 Float SDS 4  12*nscan - - degree Angle between the local pixel geodetic zenith and the direction to the satellite. This angle is given for every twentieth high resolution pixel along a scan: pixel 1, 21, 41, ... , 201, 208.
Low Resolution Channels Integer SDS 2  7*104*nscan (T-100)*100 - K Low Resolution Channels bright temperature (K) reduced by 100K, multiplied by 100.
High Resolution Channels Integer SDS 2  2*208*nscan (T-100)*100 - K High Resolution Channels bright temperature (K) reduced by 100K, multiplied by 100.


TRMM 1B11 can be accessed and ordered using the Goddard DISC's TRMM Data Search and Order System at http://disc.sci.gsfc.nasa.gov/data/datapool/TRMM_DP/01_Data_Products/01_Orbital/02_Tmi_Brtemp_1B_11/ .

Appendix

TRMM 1B11 Scan Time
Name Format Description
Year 2-byte integer 4-digit year, e.g., 1998
Month 1-byte integer The month of the Year
Day of Month 1-byte integer The day of the Month
Hour 1-byte integer The hour (UTC) of the Day
Minute 1-byte integer The minute of the Hour
Second 1-byte integer The second of the Minute
Day of Year 2-byte integer The day of the Year


TRMM 1B11 Low Resolution Channels
Channel Frequency Polarization
1 10 GHz Vertical
2 10 GHz Horizontal
3 19 GHz Vertical
4 19 GHz Horizontal
5 21 GHz Vertical
6 37 GHz Vertical
7 37 GHz Horizontal


TRMM 1B11 High Resolution Channels
Channel Frequency Polarization
8 85 GHz Vertical
9 85 GHz Horizontal


TRMM 1B11 Calibration
Name Format Range Description
Hot Load Temperature[3] 3 x 2-byte integer 0 ~ 400 K The physical temperatures, in degrees Kelvin, for the 3 temperature sensors attached to the hot load. This temperature is reduced by 80 K, multiplied by 100, and stored in the file as a 2-byte integer. Stored value = (T - 80) * 100.
Hot Load Bridge 2-byte integer 0 ~ 4095 The positive bridge voltage of the hot load bridge reference.
Hot Load Bridge Reference Near Zero Voltage 2-byte integer 0 ~ 4095 The near zero voltage of the hot load bridge reference.
85.5 GHz Receiver Temperature 2-byte integer -273.15 ~ 126.85 °C The receiver shelf temperature of the 85.5 GHz channel. This temperature is increased by 200, multiplied by 100, and stored in the file as a 2-byte integer.
Top Radiator Temperature 2-byte integer -273.15 ~ 126.85 °C The temperature of the top of the radiator channel. This temperature is increased by 200, multiplied by 100, and stored in the file as a 2-byte integer.
Automatic Gain Control [9] 9 x 1-byte integer 0 ~ 15 Automatic gain control for the 9 channels in counts.
Calibration Coefficient A [9] 9 x 4-byte float - Calibration coefficient A (degrees Kelvin / counts) for the 9 channels. Coefficient A for each channel is used in the following equation to convert counts, C, to antenna temperature, TA:   TA = A*C + B
Calibration Coefficient B [9] 9 x 4-byte float - Calibration coefficient B (degrees Kelvin) for the 9 channels. Coefficient B for each channel is used in the following equation to convert counts, C, to antenna temperature, TA:   TA = A*C + B

     
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  • Last updated: Sep 18, 2009 10:32 AM ET