NASA Activities in Support of an Advanced Altimeter Mission Tony Freeman

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NASA Activities in Support of an Advanced
Altimeter MissionTony Freeman

• October 2006

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Current Status

• WSOA was descoped from the OSTM mission in 2005
• In May 2006, the acting division manager for
  Earth Science at HQ, Bryant Cramer, commissioned
  a study of a new advanced altimeter mission
• Study is the 1st (of several) done in
  anticipation of decadal survey results
• Mission objectives were to include land and ocean
  applications
• Study was completed at the end of summer
• Since then, three joint meetings involving NASA,
  NOAA and the Navy have been held - next meeting
  in late November
• All three agencies need a follow-on altimeter
  after OSTM, which launches in 2008 and is
  expected to last 5 years
• All 3 agencies require backwards compatibility
  with the TOPEX/Poseidon/
• Jason-2/OSTM climate data records, i.e. global
  sea level
• An additional driver for NASA is to further our
  understanding of the Earth system through
  advances in measurement capability
• The advanced altimeter study resulted in a
  mission concept that can meet the requirements of
  all three agencies at reasonable cost

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Mission Concept

• Instruments
• Ka-band wide-swath radar altimeter (1-2 km
  resolution)
• Ku-band nadir altimeter
• 3-freq. water vapor radiometer
• GPS for POD
• Laser retroflector for POD

• Orbit
• 993 km altitude, 78 deg inclination
• 21-day exact repeat, 10.5 day revisit
• Delta II launch

• Science Objectives
• Sea surface height measurements (continue the
  Jason/TOPEX series)
• Study mesoscale phenomena
• Ocean bathymetry (surface slopes)
• Land surface water (hts. gradients)

• Programmatics
• NASA/NOAA/Navy partnership
• Currently no US altimeter planned after Jason-2
• Possible Eumetsat/CNES roles
• Launch date 2012 for continuity with Jason-2
• 5-year mission
• Mission Cost 500M (FY 06)

• New technology
• Wide-swath altimeter is a SAR interferometer
• Onboard processing

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1- Requirements Traceability

• Science requirements are derived from three
  primary mission concepts submitted to the NRC
  decadal survey RFI
• The WatER mission
• The Hydrosphere Mapper mission
• The Bathmetry ABYSS mission
• Navy and NOAA requirements are derived from
• Navy Altimeter Requirements, Jacobs, G. A. et al,
  Naval Research Laboratory, NRL/FR/7320--99-9696,
  Nov. 1999
• NPOESS Integrated Operational Requirements
  Document-II, January 2002

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NASA Requirements Traceability Matrix (1 of 2)
Surface WaTER
Sea Surface Topography
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NASA Requirements Traceability Matrix (2 of 2)

• References
• WatER The Water Elevation Recovery Satellite
  Mission, Response to the National Research
  Council Decadal Survey Request for Information,
  Doug Alsdorf1, Ernesto Rodriguez2, Dennis
  Lettenmaier3, and Jay Famiglietti4 1Ohio State
  Univ., 2NASA JPL, 3Univ. of Washington, and
  4Univ. of California, Irvine
• The WatER Mission, www.geology.ohio-state.edu/wate
  r
• The Global Hydrosphere Mapper, Response to the
  National Research Council Decadal Survey Request,
  L-L. Fu, E. Rodriguez, Jet Propulsion Laboratory,
  California Institute of Technology
• ABYSS-Lite A radar altimeter for bathymetry,
  geodesy and mesoscale oceanography, Smith et. al.
  2005
• Altimetric BathmetrY from Surface Slopes, A
  Proposal in response to NASA AO01-OES-01, July
  20, 2001, Principal Investigator Dr. Walter H.
  F. Smith

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Navy Requirements

• Sea Surface height, atmospheric correction
  parameters, and orbit solutions are required
  within 48hours. Wave heights are required within
  3 hours.
• The required instrument white noise level must be
  below 3 cm rms.
• The required total range error must be under 5 cm
  (peak error) after all atmospheric corrections
  are applied.
• Required real time orbit solutions must contain
  under 1 m error at 1 cycle per satellite orbit
  revolution (cpr) and less than 2 cm integrated
  errors at higher frequencies.
• An exact repeat orbit must be required, and the
  satellite must be held to within a 1 km swath of
  a predefined ground track.
• The required repeat period must not be less than
  20 days
• A minimum of one instrument is required. With
  only one instrument, this data must be used in
  conjunction with systems such as MODAS and NRL
  Layered Ocean Model (NLOM).
• Two altimeter are recommended on the NPOESS
  Polar-Orbiting Operational Environmental
  Satellite System (NPOESS) for error reduction and
  redundancy.
• Major tidal constituents should not be aliased to
  frequencies that contain significant ocean
  variability. These frequencies include the
  annual, semi-annual, and mean.

Source Navy Altimeter Requirements, Jacobs, G.
A. et al, Naval Research Laboratory,
NRL/FR/7320--99-9696, Nov. 1999. "The NPOESS
IORD-II contains approved/validated altimeter
requirements that adequately define the Navy's
needs however, recent studies show that Navy
would consider an Exact Repeat Period threshold
of slightly greater than the currently cited 20
days." Cmdr. Mark Gunzelman, personal
communication, Aug 2006
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NPOESS Requirements
Source NPOESS Integrated Operational
Requirements Document-II, January 2002
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NPOESS Requirements
Source NPOESS Integrated Operational
Requirements Document-II, January 2002
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5- Mission Concept- Orbit Parameters

• 78 degrees inclination.
• Exact repeating groundtrack after 21 days (286
  orbits at 993km).
• This leaves 17x100km diamond-shaped areas (see
  graphic) not covered (1 of area on earth in
  -30deg lat 0.5 -78deg Lat.)
• Orbit will be shifted in longitude after 1.5
  years to fill gaps for bathymetry science
  coverage.
• 993 km altitude was chosen to provide an even
  distribution of coverage during cycle
  completion. Range of altitude explored 800 to
  1000km.

Ref Francois Rogez (JPL) this study may 2003
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5- Mission Concept Orbit Parameters Coverage
map after 21 days

• After 21 days, 286 swaths are uniformly
  distributed in longitude, leaving gaps of 17 km
  between swaths at the equator.
• Adding up the coverage from ascending and
  descending passes leaves diamond shaped gaps with
  a cumulative area measuring about 800k m2 at the
  equator.
• The gaps disappear above
• 30 deg latitude.
• All coverage Gaps are
• filled when the orbit
• is shifted at 1.5 yr
• Intervals over
• mission life

Maps near the equator showing the 120km swath and
the 17 km gaps. A 1 degree lat/lon grid is shown
with dotted red lines.
Ref Francois Rogez (JPL) this study
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10- Key Instrument Performance Parameters
Ka-Band Interferometer Performance Summary
4/18/06
Ref Louise Veilleux Advanced Altimeter Mission
Study, (JPL) April 2006
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10- Key Instrument Performance Parameters Ku
C-Band Altimeter Radiometer Summary
4/18/06
Ref Louise Veilleux Advanced Altimeter Mission
Study, (JPL) April 2006
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Science Measurement Requirements

• Continues the TOPEX/Jason/OSTM record while
  adding new capabilities

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Summary

• Study Conclusions
• Trade study examined many options
• An advanced altimeter mission can meet the
  diverse requirements of NASA, the Navy and NOAA
• Estimated cost to each agency is less than a
  stand-alone conventional altimeter mission
• International partnering arrangement with
  CNES/Eumetsat in the mode of Jason-1 is feasible
• For a late 2011 launch and overlap with OSTM
  (Jason-2), need a Phase A start in 2007
• gt Decision point shortly after release of
  decadal survey