http://daac.gsfc.nasa.gov/CAMPAIGN_DOCS/TOGA/ammr.html Airborne Miltichannel Microwave Radiometer (AMMR) [colorbar] [ftp access icon]To access AMMR data on FTP. [colorbar] 1. GENERAL INFORMATION The AMMR radiometer package was part of the NASA/TOGA COARE Campaign. It was flown onboard the DC-8 between January 12 to February 24, 1994 under the direction of Dr. Jim Wang of NASA Goddard Space Flight Center. The production and distribution of this data set are being funded by NASA's Mission To Planet Earth Program. The data are not copyrighted, however we request that when you publish data or results using these data, please acknowledge as follows: The authors would like to thank the Microwave Sensors Branch (Code 975) and the Distributed Active Archive Center (Code 902.2) at the Goddard Space Flight Center, Greenbelt, MD 20771 for the production and distribution of these data, respectively. These Activities are sponsored by NASA's Mission to Planet Earth Program. 2. Instrument Information 2.1 Instrument Mission and Objectives. AMMR measures thermal microwave emission (in degrees Kelvin of brightness temperature) from surface and atmosphere. For TOGA COARE, the AMMR (with frequencies between 10 and 100 GHz) was used for measurements of hydrometeors associated with tropical convective systems. Radiometers at 18, 21, 37 and 92 GHz are comparable to the frequencies on the Special Sensor for Microwave/Imager (SSM/I) onboard the Defense Meteorological Satellite Program (DMSP) satellite. Where aircraft flights coincide with SSM/I overpasses over the COARE domain, comparisons between satellite and AMMR sensors at different resolutions are proposed to study beam filling effect. 2.2 Instrument Geometry. The AMMR package is made up of AMMR-1 and AMMR-2. AMMR-1 consists of single-beam, microwave radiometers operating at 18.7, 18.7, 21 and 37 GHz, all viewing through a nadir port of the aircraft, therefore withan incidence angle of 0 when the aircraft was on level flight. The two channels at 18.7 GHz should be seeing the same scene and brightness. AMMR-2 also consists of single-beam, microwave radiometers operating at 10, 21, 37 and 92 GHz. These radiometers were installed in the left windows of the DC-8 aircraft and viewed the scene at an incidence angle of 45 degrees in level flight. 2.3 Principles of Operation. The 37 and 92 GHz radiometers were dual-polarized. Georgia Institute of Technology operated the 92 GHz radiometer and is responsible for the calibration of the data. The 92 GHz data will be included in this AMMR data set when they are submitted to the Goddard DAAC. The spatial resolution of the data is between 1.5 to 2 Km. The temporal sampling is 1 scan per second. Following are the key components of these sensor assemblies and their characteristics: Inst Channel Sensitivity Beamwidth View loc & angle 18 GHz 0.5 K 6 Deg. Nadir AMMR-1 21/37 0.5 6 Nadir 37 0.5 6 Window(45deg),H,V-pol 92 1.0 2 Window(45deg),H,V-pol AMMR-2 21 1.0 6 window(45deg),H-pol 10 1.0 6 Window(45deg),H-pol 3. Data Organization 3.1 General Characteristics. The AMMR instruments were operational for all thirteen mission flights of the DC-8 during the TOGA COARE Campaign yielding twenty six ASCII data files (13 each for AMMR-1 and AMMR-2). The total data volume is 45 MB. AMMR files are named Adddhhmm.AR1 (for AMMR-1) and Gdddhhmm.AR2 (for AMMR-2) where ddd is the Julian day, hh is the hour, and mm is the minute the instrument was turned on for the flight. 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 defaulted to radiation unless convection was forecast in the target area. Date(UTC) ER-2 DC-8 AMMR1 File AMMR2 File Objective Flight Flight Jan 11-12 93-053 93-01-06 A0112140.AR1 G0112140.AR2 Radiation Jan 17-18 93-054 93-01-07 A0172307.AR1 G0172307.AR2 Convection Jan 18-19 93-055 93-01-08 A0191338.AR15 G0180140.AR2 Convection Jan 25-26 93-056 93-01-09 A0252331.AR1 G0252330.AR2 Radiation jan 31-Feb 1 93-057 93-01-10 A0312207.AR1 G0312312.AR2 Radiation Feb 4 93-060 93-01-11 A0351439.AR1 G0351441.AR2 Convection Feb 6 93-01-12 A0371431.AR1 G0371432.AR2 Convection Feb 7 93-061 Feb 8-9 93-062 93-01-13 A0391822.AR1 G0391823.AR2 Convection Feb 10-11 93-063 93-01-14 A0411859.AR1 G0411900.AR2 Convection Feb 17-18 93-01-15 A0481850.AR1 G0481840.AR2 Convection Feb 20-21 93-065 93-01-16 A0511909.AR1 G0511912.AR2 Convection Feb 22-23 93-066 93-01-17 A0531909.AR1 G0531912.AR2 Convection Feb 23-24 93-067 93-01-18 A0542010.AR1 G0542009.AR2 Radiation 3.2 Data Format There are 10 parameters in each file: * Scan number * Month * Day * Hour * Minute * Second * Brightness temperatures in degrees Kelvin at 18.7 GHz, 18.7 GHz, 21 GHz, and 37 GHz Latitude, Longitude, altitude and aircraft attitude information are not present in these quick-look data files, but may be obtained from the DC-8 DADS data set, also available on FTP (See Section 4: DATA ACCESS). The AMMR data files are formatted as follows: Sample of AMMR-1 Data File scan# mm dd hr mm ss 18.7GHz 18.7GHz 21GHz 37GHz 1 2 8 18 22 37 284.15 286.65 284.46 286.71 2 2 8 18 22 38 285.74 288.10 284.08 287.97 Sample of AMMR-2 Data File scan# mm dd hr mm ss 18.7GHz 18.7GHz 21GHz 37GHz 1 2 10 19 0 7 119.95 104.78 201.66 151.80 2 2 10 19 0 8 119.69 104.34 201.22 151.79 4. Data Access 4.1 AMMR Data Online [ftp access icon]AMMR_1 data on FTP. [ftp access icon]AMMR_2 data on FTP. [ftp access icon]DC-8 DADS data on FTP. 4.2 To Order AMMR on Tape Please request AMMR data on tape from TOGA COARE User Services. You may also download instructions for reading your tapes.. 5. Quality Assessment The calibration of the radiometers is based on pre-flight and post-flight surface measurements by pointing the antennas at a nearly perfect absorber (emissivity ~ 1) at room and liquid nitrogen temperatures and the in-flight ocean surface observation with dropsondes. The radiometric accuracy is estimated to be about +/- 3 K, which is adequate for rain rate measurements. The data producers consider the second 18.7 GHz channel of AMMR-1 (column 8 of the data file) and the second 10 GHz channel of AMMR-2 (column 8 of the data file) to be sufficiently noisy that they may be disregarded. The noise threshold for the AMMR is 1 degree Kelvin. Noise saturation did not occur during the TOGA COARE mission. Radiative transfer calculations were made (using code developed by Colorado State University) with assumed hydrometeor profiles to match the brightness temperatures measured by AMMR (at 20 km), AMMS (at 11 km) and AMMR-1 (at 11 km) over precipitating regions on January 19, 1993. Calculated results matched the measurements well. 6. Points of Contact For TOGA COARE user services, please contact: Pat Hrubiak (Goddard DAAC) Code 902, NASA Goddard Space Flight Center Greenbelt, Maryland 20771 Internet: hrubiak@daac.gsfc.nasa.gov (301) 301-614-5165 (voice) (301) 301-614-5268 (fax) For detailed information on instrument and data, please contact: Principal Investigator: James R. Wang Code 975, NASA Goddard Space Flight Center Greenbelt, MD 20771 Internet: wang@sensor.gsfc.nasa.gov (301) 301-286-8949 (voice) (301) 301-286-1761 (FAX) Co-Investigator: Paul Racette Code 975, NASA Goddard Space Flight Center Greenbelt, MD 20771 Internet: per@meneg.gsfc.nasa.gov (301) 301-286-9114 (voice) (301) 301-286-1762 (Fax) 7. Data Status/Plan The AMMR data first became available on DAAC public FTP in May, 1994. See other sub-directories of the FTP directory "toga_coare" for other TOGA COARE data sets. 8. References NASA/TOGA COARE Science Data Workshop II Proceedings, March 15-17, 1994, FIRE Project Office, NASA Langley Research Center, Mail Stop 483, Hampton, VA 23666. J. R. Wang and A. Chang, 1990: Retrieval of water vapor profiles from microwave radiometric measurements near 90 and 183 GHz. J. Appl. Meteor., 29(10), 1005-1013. ---------------------------------------------------------------------------- Comments on the AMMR site [TOGA COARE home icon] Home ---------------------------------------------------------------------------- Last update:Thu Apr 24 11:25:32 EDT 1997 Page Author: Pat Hrubiak -- hrubiak@daac.gsfc.nasa.gov Web Curator: Daniel Ziskin -- ziskin@daac.gsfc.nasa.gov NASA official: Paul Chan, DAAC Manager -- chan@daac.gsfc.nasa.gov