Dr. Robert L. Bernstein and Dr. Kota Prasad - SeaSpace Corporation

Dr. David Sandwell and Dr. Bernard Minster - Scripps Institution of Oceanography

Contents:

Objectives

Overall Plan

SBIR Phase II Progress Report - December 1997

First Data Acquisition on January 13, 1999 from ERS-2

• To routinely acquire SAR data from passes across the San Andreas fault zone in Southern California in order to to monitor crustal deformation in this tectonically-active area.
• To integrate Interferometric SAR data with an array of 150 continuously-operating GPS recievers to increase the accuracy of the interferogram. This involves the deployment of radar corner reflectors at selected GPS sites to aid the calibration of the phase.
• To acquire SAR data along coastal areas of California and Baja California in order to to study mixing processes in the California Current.
• To extend the overall coverage of ERS-2 to include a large portion of Mexico and much of the Eastern North Pacific Ocean. In addition regular acquisition over southwestern North America would reduce the burden at the Prince Albert, Canada site enabling them to improve their coverage of Arctic areas.

SIO is currently developing an X-band down-link facility, located on the SIO campus, by upgrading an existing 5-m satellite dish and electronics. In the past, X-band data acquisition been done with a larger dish antenna (~10 m) and at a much higher cost. Thus some engineering R&D is needed to compensate for the smaller aperture by taking advantage of state-of-the-art electronic technology. SeaSpace Corporation, San Diego, CA is developing the acquisition hardware and software. Both SeaSpace and SIO scientists are developing the SAR processing software and SAR data distribution system. NASA (50%), the State of California (25%) and SeaSpace/SIO (25%) are funding this project. The funding for the system is now complete and construction is in progress. The overall tasks follow:

• SIO provides the existing 5-m Scientific Atlanta dish as well as a small building adjacent to the antenna. Some funding from the SIO director's office have been used for refurbishing the antenna and building as well as other infrastructure items such as network connections. (completed 5/96)

• SIO provides office space for SeaSpace personnel, network access and some access to other major computer items like mass storage devices. (completed 12/96)

• SeaSpace provides the technical expertise to design and construct the facility. This involves upgrading the antenna and tracking system, selecting; the antenna feed, the low-noise amplifier, the bit synchronizer, and the specialized boards for process and storage of the data. (Dr. Kota Prasad is the SeaSpace engineer working on the project).

• SeaSpace and SIO will work together on developing the SAR processor and interferometric code as well as the systems for data archive, data processing, and data distribution. A re-write of a Stanford/JPL SAR processor from FORTRAN to C is fully tested. The 8-terabyte Storage Technology disk/DLT system at IGPP is archiving a variety of geophysical data. The intent is not to become a major data acquisition and archive facility that will service all scientific/commercial needs in western North America. Instead we wish to acquire the most scientifically interesting data sets. The SIO X-band downlink will acquire data from EOS-AM1 and other high data rate satellites.

• i. New Cables and Connectors - New cables and connectors were installed since the last reporting period. New 1/2 ( Hiliax cables (LDF4-50A) were installed between the X-band feed and the new downconverter. New bulk-head connectors were installed for connecting the cables between the feed and the pedestal. The signal gain at the feed and downconverter were tested for eliminating possible electronic interlocks. Antenna azimuth and elevation commands were issued to insure that the hiliax cables did not wrap around and attenuate the signal.
• ii. Antenna sun alignment and tracking adjustments - Sun alignment was performed on the antenna. The shadow of the X-band feed on the center of the dish was clearly marked for making measurements of the feed offset. Using these measurements coefficients were computed in degrees and later integrated into the antenna control software. This exercise improved the pointing accuracy to a considerable extent. Further changes in the antenna control software were made to minimize the antenna lag during elevation.
• iii. Signal generator - A HP signal generator was installed for generating the local oscillator (LO) frequency required for stabilizing the downconverter. The reference frequency was determined as follows: LO (MHz) = RF(MHz)-375/75 Where RF is the downlink frequency in MHz for the desired X-band telemetry, 375 is the IF frequency, and 75 is the multiplier for the reference input. The LO for ERS-2 and RADARSAT were computed as 103.53 MHz and 103.06 MHz respectively. The external LO reference level at the downconverter was set at 0.0 dBm(3.0 dBm.
• iv. RF integration - The X-band demodulator, bit-synchronizer, and the HP signal generator were mounted on a vertical chassis. The chassis was fitted with an exhaust fan on the top panel and a air-blower at the bottom for cooling the system. The bit-synchronizer was installed with a plug-in module for RADARSAT/ERS-2. The downconverted RF signal was used as input to the demodulator. The clock and data from the bit-synchronizer was used for testing the signal strength.
• v. ERS-2 and RADARSAT tracking - The Sun-Ultra-II workstation has been setup to receive updated orbital elements for ERS-2 and RADARSAT satellites once every day. Passes were scheduled for ERS-2 satellite initially and later RADARSAT was added to the list. We achieved demodulator and bit-synchronizer signal lock for both ERS-2 and RADARSAT satellites. A spectrum analyzer was used for observing the signal peak, and a printer was used for copying the signal peak at various elevations. We were particularly interested in observing the elevation angle when a solid signal lock was on the bit-synchronizer. We enclose representative plots of the spectrum analyzer output both for ERS-2 and RADARSAT recorded during our recent tracking tests. The plots show adequate gain above the normal for both the satellites.

• The development of the high-speed frame synchronizer that can handle data rates up to 150 Mbps is 90% complete . Four PC boards have been fabricated. Tests have been completed for writing data to disk using the Simbios SCSI processor. Instead of a Sun Ultra-II, we plan to take advantage of the new Sun Ultra 30 workstation for integrating our frame-synchronizer. The Sun Ultra 30 offers 4 full-sized PCI 32-/64-bit slots and has a clock speed of 296 MHz. We plan to use simulated data to test the 150 Mbps frame synchronizer.

• The initial version of the SAR processor had the capability to ingest and process only ERS-1 and ERS-2. Recently, a RADARSAT front-end parser has been added to SAR processor. Other features added to the processor include raw data ingest from CD-ROM and ingestion of raw data in CEOS data format.

• We will concentrate on testing the frame-synchronizer extensively. Frame formats for both ERS and RADARSAT will be used to program the frame-synchronizer. Testing will also continue for handling rapid disk write code using raw synthetic data generated at a data rate of 150 Mbps. Once we are satisfied with the frame-synchronizer's ability to handle high data rates, we will input clock and data from the bit-synchronizer and test the framing capability of the system. This will form a critical step in our system integration and we expect to complete testing during the first quarter of 1998.