Lockwood, Dennis W. | Engineering Papers

NASA NTRS2006

TOPEX Radar Altimeter Engineering Assessment Report Final Update-Side B Turn-On to End-of-Mission on October 9, 2005

This is the thirteenth and final report in a series of TOPEX Radar Altimeter Engineering Assessment Reports. The initial TOPEX Radar Altimeter Engineering Assessment Report, in February 1994, presented performance results for the NASA Radar Altimeter on the TOPEX/POSEIDON spacecraft, from its launch in August 1992 to February 1994. Since the time of that initial report and prior to this report, there have been eleven interim supplemental Engineering Assessment Reports, issued in March 1995, May 1996, March 1997, June 1998, August 1999, September 2000, June 2001, March 2002, May 2003, April 2004 and September 2005. The sixth supplement in September 2000 was the first assessment report that addressed Side B performance, and presented the altimeter performance from Side B turn-on until the end of calendar year 1999. This report extends the performance assessment of Side B to the final collection of data on October 9, 2005, and includes the performance assessment of Jason-1, the TOPEX follow-on mission, launched on December 7, 2001. This report provides some comparisons of Side A and Side B performance.

Lockwood, Dennis W.↗

NASA NTRS2003

GEOSAT Follow-On (GFO) Altimeter Document Series: Version 1 - Volume 5

This document is a compendium of the WFF GFO Software Development Team's knowledge regarding of GDO CAL/VAL Data. It includes many elements of a requirements document, a software specification document, a software design document, and a user's guide. In the more technical sections, this document assumes the reader is familiar with GFO and its CAL/VAL Data.

Lockwood, Dennis W.↗

NASA NTRS2003

TOPEX SDR Processing, October 1998

This document is a compendium of the WFF TOPEX Software Development Team's knowledge regarding Sensor Data Record (SDR) Processing. It includes many elements of a requirements document, a software specification document, a software design document, and a user's manual. In the more technical sections, this document assumes the reader is familiar with TOPEX and instrument files.

Lee, Jeffrey E.↗

NASA NTRS2002

GFO Altimeter Engineering Assessment Report

The U.S. Navy's Geosat Follow-On (GFO) Mission, launched on February 20, 1998, is one of a series of altimetric satellites which include Seasat, Geosat, ERS-1, and TOPEX/POSEIDON (T/P). The purpose of this report is to document the GFO altimeter performance determined from the analyses and results performed by NASA's GSFC and Wallops altimeter, calibration team. It is the second of an anticipated series of NASA's GSFC and Wallops GFO performance documents, each of which will update assessment results. This report covers the performance from instrument acceptance by the Navy on November 29, 2000, to the end of Cycle 20 on November 21, 2001. Data derived from GFO will lead to improvements in the knowledge of ocean circulation, ice sheet topography, and climate change. In order to capture the maximum amount of information from the GFO data, accurate altimeter calibrations are required for the civilian data set which NOAA will produce. Wallops Flight Facility has provided similar products for the Geosat and T/P missions and is doing the same for GFO.

Lockwood, Dennis W.↗

NASA NTRS2002

GEOSAT Follow-on (GFO) Altimeter Document Series: GFO Altimeter Engineering Assessment Report, Version 1 - Volume 3

The U.S. Navy's Geosat Follow-On (GFO) Mission, launched on February 20, 1998, is one of a series of altimetric satellites which include Seasat, Geosat, ERS-1, and TOPEX/POSEIDON (T/P). The purpose of this report is to document the GFO altimeter performance determined from the analyses and results performed by NASA's GSFC and Wallops altimeter, calibration team. It is the second of an anticipated series of NASA's GSFC and Wallops GFO performance documents, each of which will update assessment results. This report covers the performance from instrument acceptance by the Navy on November 29, 2000, to the end of Cycle 20 on November 21, 2001. Data derived from GFO will lead to improvements in the knowledge of ocean circulation, ice sheet topography, and climate change. In order to capture the maximum amount of information from the GFO data, accurate altimeter calibrations are required for the civilian data set which NOAA will produce. Wallops Flight Facility has provided similar products for the Geosat and T/P missions and is doing the same for GFO.

Hancock, David W., III↗

NASA NTRS2001

GEOSAT Follow-on (GFO) Altimeter Document Series: GFO Altimeter Engineering Assessment Report: From Launch to Acceptance, 10 February 1998 to 29 November 2000 - Volume 1

The US Navy's Geosat Follow-On (GFO) Mission, launched on February 10, 1998, is the latest in a series of altimetric satellites which include Seasat, Geosat, ERS-1, and TOPEX/POSEIDON (T/P). The purpose of this report is to document the GFO altimeter performance determined from the analyses and results performed by the NASA/GSFC/Wallops altimeter calibration team. It is the first of an anticipated series of NASA/GSFC/Wallops' GFO performance documents, each of which will update assessment results. This report covers the performance from launch to instrument acceptance by the Navy on November 29, 2000. Data derived from GFO will lead to improvements in the knowledge of ocean circulation, ice sheet topography, and climate change. In order to capture the maximum amount of information from the GFO data, accurate altimeter calibrations are required for the civilian data set which NOAA will produce. Wallops Flight Facility has provided similar products for the Geosat and T/P missions and is doing the same for GFO.

Hancock, David W., III↗

NASA NTRS1990

Effects of height acceleration on Geosat heights

A radar altimeter tracking loop, such as that utilized by Geosat, produces height errors in the presence of persistent height acceleration h(a). The correction factor for the height error is a function of both the loop feedback parameters and the height acceleration. The correction, in meters, to the sea-surface height (SSH) derived from Geosat is -0.16 h(a), where h(a) is in m/sec per sec. The errors induced by accelerations are produced primarily by changes in along-track geoid slopes. The nearly circular Geosat orbit and dynamic ocean topography produce small h(a) values. One area studied in detail encompasses the Marianas Trench and the Challenger Deep in the west central Pacific Ocean. Histograms of SSH corrections due to range accelerations have also been determined from 24-hour segments of Geosat global data. The findings are that 20 percent of the Geosat measurements have acceleration-induced errors of 2 cm or more, while 8 percent have errors of 3 cm or more.

Hancock, David W., III↗

NASA NTRS1990

Effects of islands in the Geosat footprint

The presence of land within a radar altimeter's footprint may contaminate its tracking performance and perturb the nadir oceanographic signal. A study has been performed which examines the effects of small mid-ocean islands on the Geosat tracker. The surface return waveforms, as well as the altimeter measurements, have been analyzed. Open-ocean waveforms have been compared with waveforms containing land reflections; they differ perceptibly. Computations could be performed, based on a combination of waveform data, altimeter signal strength, and sea surface heights, to detect contaminated sea-surface height values for subsequent editing.

Brooks, Ronald L.↗