The ESMR instrument, which was mounted on NASA's DC-8 aircraft for the TOGA COARE Field Experiment, is a scanning radiometer that measures brightness temperatures in degrees Kelvin. It was operational during 13 mission flights of the DC-8 between January 11 and February 26, 1993 under the direction of Dr. Thomas Wilheit of Texas A & M University.
2.1 Science Objectives The objective for the ESMR instrument in the TOGA COARE Campaign is to provide observations to develop better radiative transfer models for rainfall retrieval algorithms to be used in the development of the TRMM research paradigm.
2.2 Principles of Operation The ESMR instrument is a 19.35 GHz scanning radiometer mounted aboard NASA's DC-8 aircraft.
2.3 Instrument Geometry. The ESMR radiometer is nadir-mounted in the aircraft and scans in a plane perpendicular to the direction of flight with a swath of +/-50 degrees from nadir. Beam position (BP) 20 is at nadir during level flight; BP 1 is 50 degrees to the left, and BP 39 is 50 degrees to the right. The beam positions are distributed in equal divisions of the sine of the scan angle.
When the pitch and roll of the plane are negligible, a simple algorithm can be used to obtain the latitude and longitude at each BP.
If we define:
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The following table relates ESMR data files to ER-2 and DC-8 flight numbers and dates for the 13 mission flights of the NASA/TOGA COARE campaign. The objectives column is included for the convenience of the user; the mission objective was convection when it was forecast in the target area and radiation when it was not.
| Date(UTC) | ER-2 Flight | DC-8 Flight | ESMR File | Objective |
|---|---|---|---|---|
| Jan 11-12 | 93-053 | 93-01-06 | 011.tbn | Radiation |
| Jan 17-18 | 93-054 | 93-01-07 | 017.tbn | Convection |
| Jan 18-19 | 93-055 | 93-01-08 | 019.tbn | Convection |
| Jan 25-26 | 93-056 | 93-01-09 | 025.tbn | Radiation |
| Jan 31-Feb 1 | 93-057 | 93-01-10 | 031.tbn | Radiation |
| Feb 4 | 93-060 | 93-01-11 | 035.tbn | Convection |
| Feb 6 | 93-01-12 | 037.tbn | Convection | |
| Feb 7 | 93-061 | Convection | ||
| Feb 8-9 | 93-062 | 93-01-13 | 039.tbn | Convection |
| Feb 10-11 | 93-063 | 93-01-14 | 041.tbn | Convection |
| Feb 17-18 | 93-065 | 93-01-15 | 048.tbn | Convection |
| Feb 20-21 | 3-065 | 93-01-16 | 051.tbn | Convection |
| Feb 22-23 | 93-066 | 93-01-17 | 053.tbn | Convection |
| Feb 23-24 | 93-067 | 93-01-18 | 057.tbn | Radiation |
3.2 Data Format
The TbN data format is as follows
| bytes | Type | variable |
|---|---|---|
| 1-39 | unsign 1 byte | Brightness Temp for each BP (add 100.) |
| 40 | Hour | |
| 41 | Minute | |
| 42 | Seconds (integer part) | |
| 43 | Hundreths of seconds | |
| 44-45 | signed 2-byte | Julian Day |
| 46-47 | Latitude(integer part) | |
| 48-49 | 1/10000ths of latitude | |
| 50-51 | Longitude (integer part) | |
| 52-53 | 1/10000ths of longitude | |
| 54-55 | Altitude (tens of feet) | |
| 56-57 | Heading (tenths of degrees) | |
| 58-59 | Roll (tenths of degrees) | |
| 60-61 | Pitch (tenths of degrees) | |
| 62-64 | - | Empty |
| Note: the latitude and longitude fractions share the same sign; to obtain either variable, simply sum the integer and fractional parts without manipulating the signs. All of the integers are standard MS-DOS format | ||
3.3 ESMR Browe Images A series of GIF images which are 256-color pictures of the data, made from screenshots of the data viewing program. The GIF images are labelled with the Julian Day, hour and minute that the data starts, in the form DDDHHMM.GIF.
The GIFs are 800x600, and can be viewed with any image viewing application, on any platform. If you do transfer the files to another platform, remember to transfer them in binary (8-bit) format.
There are GIF images for all of the high-priority convection legs and days specified by Drs. Ed Zipser, Barry Nolan, and others at the August 3-6 TOGA COARE conference in San Diego.
4.1 The ESMR Data Products Online.
ESMR Binary Data
ESMR Browse Images
4.3 Software. 4.3.1 DOS Software. Read software in Turbo Pascal (RDTBNAV) was submitted by the ESMR instrument team. The program reads a specified record from an ESMR binary data file and displays it to the pc screen. Program DISP_TB displays an ESMR image file to the pc screen.
Display software used by the PI in processing the data has also been made available. It runs in a DOS environment and requires a Super VGA video card based on the Tseng chipset or a VESA standard compatible video card with appropriate drivers.
4.3.1 DOS Software. Read software in Turbo Pascal (RDTBNAV) was submitted by the ESMR instrument team. The program reads a specified record from an ESMR binary data file and displays it to the pc screen. Program DISP_TB displays an ESMR image file to the pc screen.
4.3.2 UNIX Software. Program esmr_read.c was created by the GSFC DAAC to provide the functionality of the original Pascal read program to UNIX users. Porting the ESMR data set from a PC to the DAAC's Silicon Graphics machines required a byte swap when loading 2-byte data values into integers, an implementation-dependent feature that may not be required on other systems. The program is self documenting.
A validation file (ESMR.dat) displaying correct values from the first ten records in data file 011.tbn is offered to assist UNIX users in adapting program esmr_read.c to their environments. It resides with the UNIX software.
In general, if the pitch or roll of the aircraft is greater than 5 degrees (pitch and roll are recorded in the data once for each scan) the data is not considered reliable, particularly at the extreme beam positions.
5.1 NAV Data 5.1.1 Times. All times are in UTC. The instrument clock was synchronized with the aircraft clock at the beginning of each flight.
5.1.2 Spatial Coordinates. Geo-referencing information was acquired from the aircraft's DADS system and is included in the data.
5.2 Noise Levels The noise threshold for this instrument is 4 Kelvin. Saturation did not occur during this campaign.
- For information about or assistance in using any NASA/TOGA COARE data, contact
- Pat Hrubiak
- EOS Distributed Active Archive Center(DAAC)
- Code 610.2
- NASA Goddard Space Flight Center
- Greenbelt, Maryland 20771
- Internet: hrubiak@disc.gsfc.nasa.gov
- 301 614-5165 (voice)
- 301 614-5268(fax)
- For detailed information about the sensor, contact the principal investigator
- T. T. Wilheit
- Department of Meteorology
- Texas A&M University
- College Station, TX 77843-3150
- Internet: Wilheit@ariel.tamu.edu
- 409 845-0176 (phone or fax)
NASA/TOGA COARE Science Data Workshop II, Proceedings of a workshop held in Albuquerque, New Mexico, March 15-17, 1994, July 1994, FIRE Project Office, NASA Langley Research Center, Mail Stop 483, Hampton, VA 23666.
Mission Summary Reports, TOGA COARE, November 1993, NASA TOGA COARE Project Office, NASA Langley Research Center, Mail Stop 483, Hampton, VA 23666
Chang, A.T.C., A. Barnes, M. Glass, R. Kakar, & T.T. Wilheit, 1993: Aircraft observations of the vertical structure of stratiform precipitation relevant to microwave radiative transfer. J. Appl. Meteor. 32, 1083-1091.
Wilheit, T.T., A.T.C. Chang and L.S. Chiu, 1991: Retrieval of Monthly rainfall indices from microwave radiometric measurements using probability distribution functions. J. Atmos. Oceanic Tech.,8, 118-136
Wilheit, T.T., {and 18 others}, 1994: Algorithms for the retrieval of rainfall from passive microwave measurements. Submitted to Reviews of Remote Sensing.
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