DATA USER'S HANDBOOK

INTRODUCTION

The formats for the various data products are described below:

1. The Sensor Data Record (SDR) provides time tagged altimeter and radiometer data. 
2. The Navy Geophysical Data Record (NGDR) appends earth location and geophysical corrections to the SDR data.
3. The NOAA Geophysical Data Record (GDR) provides an archived data set on CD ROM, updated as improved orbits
   and geophysical corrections become available.
4. The Cal/Val Formats provides the actual formats used in the calibration and validation (Cal/Val) effort.

These data sets combined are provide the information produced by GFO continuously during the mission:

1. Earth located measurement data.
2. Payload data during Calibration and Acquisition mode.
3. Payload engineering data.
4. Waveform data records during calibration mode and acquisition mode.
5. Payload operations data including the payload command log, spacecraft significant event log, and any changes in the Center of Gravity or payload configuration.
6. Waveform data over Greenland.

This handbook provides the information necessary to access and use the data: 

DATA PRODUCTION

The GFO spacecraft memory is dumped several times per day to the ground system Remote Sites. Two raw telemetry data files are constructed at the remote sites containing 1) altimeter and radiometer science data and 2) altimeter and radiometer engineering data. These files are transferred to the POC where they are maintained on-line for 7 days. Data from the GPS receiver and Doppler Beacon are transmitted to the SOC from the remote sites. Operational and Precision orbits are computed at the SOC and transmitted to the POC.

The GFO payload data is sent from the Remote Site to the POC in a POC data file, one data file per DSU dump. The POC decommutates the data contained in the POC data file and processes the data into the SDR File. The Sensor Data Record produced from each data dump includes data only when the altimeter is in Fine Track Mode. Once the SDR has been produced, the original payload data arrays are scanned and the four files (ASCII) created.  There is one file each for the altimeter data, altimeter calibration containing all full waveform data, water vapor radiometer data and the ancillary engineering data.  The engineering data is a subset of the full ancillary data set and contains only the information required to produce an SDR. In the event there is no data, a message stating "No data available" is output to the file. Engineering unit conversions (using the coefficients found in the Command & Telemetry Manual) and VTCW to UTC are the only operations done on the payload data before being written to the Cal/Val Files. Gaps in the data are not zero filled in the Cal/Val Files.

The ADFC transfers the SDR (by FTP) to the CalVal server along with the corresponding ASCII files.