L_ NASA/TM--2001-209984/VER1/VOL. 1 m GEOSAT Follow-On (GFO) Altimeter Document Series r Volume 1 GFO Altimeter Engineering Assessment Report From Launch to Acceptance 10 February 1998 to 29 November 2000 i" Version 1.0 David W. Hancock III George S. Hayne Ronald L. Brooks g.. Dennis W. Lockwood m = w March 2001 i j The NASA STI Program Office ... in Profile J Since its founding, NASA has been dedicated to CONFERENCE PUBLICATION. Collected [] the advancement of aeronautics and space papers from scientific and technical science. The NASA Scientific and Technical conferences, symposia, seminars, or other Information (STI) Program Office plays a key meetings sponsored or cosponsored by NASA. i part in helping NASA maintain this important role. SPECIAL PUBLICATION. 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Scientific and 7121 Standard Drive technical findings by NASA-sponsored Hanover, MD 21076-1320 II contractors and grantees. m [] - iF NASA/TM--2001-209984/VER1/VOL. 1 GEOSAT Follow-On (GFO) Altimeter Document Series Volume 1 GFO Altimeter Engineering Assessment Report From Launch to Acceptance 10 February 1998 to 29 November 2000 Version 1.0 David W. Hancock III George S. Hayne Observational Science Branch, Laboratory for Hydrospheric Plvcesses NASA GSFC Wallops Flight Facility, Wallops Island, Virginia 2333 7 Ronald L. Brooks Dennis W. Lockwood Raytheon ITSS NASA GSFC Wallops Flight Facility, Wallops Island, _qrginia 2333 7 2 National Aeronautics and Space Administration Goddard Space Flight Center Greenbelt, Maryland 20771 March 2001 D roll m z g up I m w 1il m W Ij Available from: NASA Center for AeroSpace Information National Technical Information Service 7121 Standard Drive 5285 Port Royal Road m Hanover, MD 2 i 076-1320 Springfield, VA 22161 Price Code: A 17 Price Code: A 10 m m II Foreword The 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). Data and results from these missions lead to vast improvements in our knowledge of ocean circulation, ice sheet topography, and cli- mate change. In order to capture the maximum amount of information from the alti- metric data, accurate altimeter calibrations are required for the GFO civilian data set which NOAA will produce. NASA/Goddard Space Flight Center/Wallops Flight Facility (GSFC/WFF) has provided these products for the Geosat and T/P missions and is doing the same for GFO. Wallops' multiple roles with regard to GFO are: • NASA Representative for Radar Altimeter Performance • Calibration Collaboration • Member of GFO Cal-Val Team • Data distribution to members of Cal-Val Team • Validate sensor-related corrections • Provide corrections for sensor changes For the latest updates on the performance of the GFO Radar Altimeter, and for accessing many of our reports, readers are encouraged to contact our WFF/GFO Home Page at http://gfo.wff.nasa.gov/ This WFF GFO Altimeter Engineering Assessment Report has been prepared by Ray- theon/ITSS under Contract NAS5-00181 with the NASA Goddard Space Flight Cen- ter, Greenbelt, Maryland. This work was performed under the direction of David W. r Hancock, III, WFF GFO Altimeter Verification Manager, Observational Science Branch, Laboratory for Hydrospheric Processes, NASA Goddard Space Flight Center, L Wallops Flight Facility, Wallops Island, Virginia, who may be contacted at (757) 824- 1238, [email protected] (e-mail), or (757) 824-1036 (fax). _m m December 2000 Page iii From Launch to Acceptance GFO Altimeter Engineering Assessment Report Foreword -- m I m 1 m W =z I From Launch to Acceptance Page iv December 2000 Acknowledgments This document includes contributions by the following members of the Wallops Flight Facility GFO Team: • David Hancock (NASA GSFC/WFF) WFF GFO Altimeter Verification Manager • George Hayne (NASA GSFC/WFF) • Anita Brenner (Raytheon ITSS/Greenbelt) • Lisa Brittingham (Raytheon ITSS) • Ronald Brooks (Raytheon ITSS) • Jeffrey Lee (Raytheon ITSS) • Dennis Lockwood (Raytheon ITSS) • Carol Purdy (Raytheon ITSS) • Ngan Tran (Raytheon ITSS) L = w December 2000 Page v From Launch to Acceptance GFO Altimeter Engineering Assessment Report Acknowledgments -- m i m 'w W l I L I m m U m I From Launch to Acceptance Page vi December 2000 I Table of Contents Foreword .......................................................... iii Acknowledgments ................................................... v Table of Contents ................................................... vii List of Figures ....................................................... ix List of Tables ....................................................... xi Section 1 Introduction 1.1 Identification of Document ............................... 1-1 1.2 Definition of a GFO Cycle ................................ 1-1 1.3 Data Flow to/from Wallops ............................... 1-1 Section 2 On-Orbit Instrument Performance 2.1 Internal Calibrations ................................... 2-1 2.2 GFO Cycle (17.05 days) Summaries ....................... 2-10 2.3 GFO Key Events ...................................... 2-12 Section 3 Assessment of Instrument Performance Y 3.1 Range Measurement Noise ............................... 3-1 3.2 GFO Sigma Naught Comparison with TOPEX ............... 3-3 3.3 GFO SWH Comparison of GFO and TOPEX ................. 3-5 3.4 Wind Speeds .......................................... 3-6 3.5 GFO Sigma0 and SWH Calibration Correction ............... 3-8 3.6 Waveform Fitting in GFO Data ........................... 3-9 3.7 GFO "Smile Patch" and its Consequences .................. 3-21 3.8 GFO Range and SWH Consequences of Thermal Change ..... 3-25 3.9 Sigma0 Blooms and Examples in GFO Data ................ 3-28 Section 4 WFF's Processing Recommendations to GFO Project 4.1 Temperature Correction for AGC .......................... 4-1 4.2 WFF Recommended Sigma0 and SWH Corrections ........... 4-3 Section 5 Engineering Assessment Synopsis 5.1 Performance Overview .................................. 5-1 fc,r 5.2 Open Issues ........................................... 5-1 Section 6 References 6.1 Supporting Documentation ............................... 6-1 Appendix A GFO Altimeter Sigma0 and SWH Calibration Correc- tion Abbreviations & Acronyms .......................................... AB-1 December 2000 Page vii From Launch to Acceptance GFO Altimeter Engineering Assessment Report Table of Contents _, "llW m m II m v m ti; = W m I i From Launch to Acceptance Page viii December 2000 W List of Figures Figure 2-1 Launch-to-Date Cal 1 Range/Temperature ................... 2-2 Figure 2-2 Period 1999-180 to 1999-229 Cal 1 Range/Temperature ........ 2-3 Figure 2-3 Period 2000-122 to 2000-190 Cal 1 Range/Temperature ........ 2-4 Figure 2-4 Period 2000-243 to 2000-277 Cal 1 Range/Temperature ........ 2-4 Figure 2-5 Launch-to-Date Cal 1 AGC ................................. 2-5 Launch-to-Date Cal 2 AGC ................................. 2-6 = Figure 2-6 Figure 2-7 Period 1999-180 to 1999-229 Cal I AGC ...................... 2-7 Figure 2-8 Period 1999-180 to 1999-229 CaI 2 AGC ...................... 2-7 Figure 2-9 Period 2000-122 to 2000-190 CaI 1 AGC ...................... 2-8 Figure 2-10 Period 2000-122 to 2000-190 Cal 2 AGC ...................... 2-8 Figure 2-11 Period 2000-243 to 2000-277 Cal 1