Gamma ISP: Reference Manual

PRC_vec

ANSI-C program: PRC_vec.c

NAME
PRC_vec extracts ERS state vectors from orbit data provided by ESA in the Precision Orbit Data (PRC) product. It places 5 state vectors in the SLC parameter file that bracket the center time of the SAR image. PRC state vectors are given at 30 second intervals.

SYNOPSIS
PRC_vec <SLC_par> <PRC> [nstate]

<SLC_par>	parameter file for SLC
<PRC>	Precision Orbit data file
[nstate]	number of state vectors (default=5, maximum=9)

EXAMPLE
PRC_vec 22331.par PRC_951021_22319_rev2 5

DESCRIPTION
PRC_vec reads ERS precision state vector files (*.prc) and extracts a specified number of state vectors that bracket the processed image data center time. The state vectors are written into the ISP SLC/PRI/MLI image parameter file along with the start time and time interval between state vectors. The PRC files consist of 130 byte ASCII records containing the Julian date and time of the state vector data, the position, velocity and attitude of the ERS sensor, and data quality information. State vectors are given on 30 second intervals. The default number of state vectors is 5 and is adequate unless multiple frame images are processed with the ISP.

The PRC data are available from an FTP server in Germany with a delay of about 1 month after data acquisition by ERS. Apply to the ESA HelpDesk at ESA ESRIN to get an account to access these data. The PRC data contain the position and velocity of the sensor in both body-fixed and inertial coordinates. Sensor attitude data is also kept with the state vectors. PRC data are available with a delay of about 1 month and cover a period of about 5-7 days each. The PRC filenames contain the date of the first state vector and the starting orbit number.

The state vectors in the SLC parameter file are used for the removal of the average phase trend in the interferogram and for determining the interferometric baseline.

SEE ALSO
typedef_ISP.h, SLC_par.