GES DISC DAAC Data Guide:
TRMM VIRS Radiance (TRMM 1B01)

THIS DOCUMENT IS AVAILABLE ON THE GES DISC WEB SITE FOR HISTORICAL INFORMATION PURPOSES ONLY. Information provided in this document may not be accurate. We recommend checking other sources related to these data or sensors to acquire reliable and updated information.

Explanation: The Dataset or Sensor Guide Document you are accessing is no longer actively maintained. The Dataset Guide Documents were created for earlier versions of the NASA EOSDIS system. The content of these documents, particularly with regard to characteristics of the data or technical descriptions of a sensor, is likely still accurate. However, information such as contact names, phone numbers, mailing addresses, email addresses, software programs, system requirements, and data access procedures may no longer be accurate. We therefore recommend searching for updated information from other sites to insure that reliable and current information is obtained.

Summary

The Level 1B product file (1B01) contains calibrated radiances and auxiliary geolocation information for each pixel in the scan. The Level 1B data are stored in the Hierarchical Data Format (HDF), which includes both core and product specific metadata applicable to the VIRS measurements. A file contains a single orbit of data with a file size of about 87 MB (uncompressed). The HDF-EOS "swath" structure is used to accommodate the actual geophysical data arrays. As in the case of the Level 1A data, there are 16 files of VIRS 1B01 data produced per day. For channels 1 and 2, Level 1B radiances are derived from the Level 1A sensor counts by computing calibration parameters (gain and offset) derived from the counts registered during space and solar and/or lunar views. New calibration parameters are produced every 1 to 4 weeks. Bands 3, 4, and 5 are calibrated using the internal blackbody and the space view. These two data points, together with a quadratic term determined pre-launch, are used to generate a counts vs. radiance curve for each band, which is then used to convert the earth-view pixel counts to spectral radiances.

For the Level 1B data, geolocation and channel data are written out for each pixel along the scan, whereas the time stamp, scan status (containing scan quality information), navigation, calibration coefficients, and satellite/ solar geometry are specified on a per-scan basis. There are in general 18026 scans along the orbit with each scan consisting of 261 pixels. The scan width is about 720 km. There are 16 files each of PR 1B01 produced per day.

Spatial coverage is between 38 degrees North and 38 degrees South owing to the 35 degree inclination of the TRMM satellite.

Contacts for Data Access Information

301-614-5224 voice
301-614-5268 fax

Email: help-disc@listserv.gsfc.nasa.gov

Data Center Identification

GSFC-TSS - Goddard Space Flight Center Distributed Active Archive Center, NASA

References:

Document Information

Document Revision Date:Fri May 17 10:10:10 EDT 2002
Document Review Date: Wed May 15 10:24:19 EDT 2002
Document Author: Hydrology Data Support Team