Transcript Advanced Altimeter Mission

NASA Activities in Support
of an Advanced Altimeter
Mission
Tony Freeman
October 2006
Advanced Altimeter Mission
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
Advanced Altimeter Mission
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)
New technology:
• Wide-swath altimeter is a SAR
interferometer
• Onboard processing
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)
Advanced Altimeter Mission
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 DocumentII, January 2002
Advanced Altimeter
Mission
NASA Requirements:
Traceability
Matrix
(1 of 2)
Surface Water
WaTER
Surface
Ca tegoryScience Objectiv e s
Scientific M easure me nt Require me nts
Instrume nt F unctiona l RequireM
me
ission
nts F unctiona l Re quirements
Le v e l 2 Data Products
Global monitoring of storage change by
m eas uring changes in w ater body
Ka-band Interferometer
WatER Sc ience O bjectives:
height and spatial extent with time.
Requirem ents: Height accuracy
Determine surfac e w ater storage Derivation of river discharge from
5c m. Slope accurac y 10urad
change and discharge to predict m eas urem ents of slope and spatial
(1cm/km ). Spatial resolution
the land s urface branch of the
extent within a hydrodynam ic m odel
finer than a 100 m posting. 120
global hydrologic cyc le; Measure as sim ilation. Revisit tim e ~ 2 w eeks in
km total s wath.
flood hydraulics; ass ess the role the tropic s and less than 1 w eek in the
of fres h w ater storage as a
Arctic .
regulator of biogeochem ical cyc les
such as c arbon and nutrients. [A] 3 year bas eline operation, w ith a 5 year 3 year reliability, with a 5 year
goal.
goal.
O rbit /repeat (14 days in the
tropic s, less than 7 days in the
Arctic ). Exac t repeat is not
required, rather sam ples
anywhere within the sw ath are
sufficient for des cribing water
height. Precise orbit
determ ination required.
Minim um 1 year, with a 3 year
baseline m iss ion, with a 5 year
goal.
Global maps of w ater surfac e
elevations and area are expected
after every period of global
coverage (e.g., ~ weekly).
Individual sw aths will be us eful for
loc al w ater m anagers.
Hydrologists need derived
products that are global maps of
water storage change and
dis charge. Hydraulic engineers
will need maps of h, dh/dt, dh/dx
and area.
In the open ocean 30 km aw ay from the
Ka-band Interferometer:
coast, the SSH accurac y shall be less
1. 5 cm precis ion with 2 km x 2
than
km resolution.
4. 6 cm (1) at wavelengths s horter than
Nadir Radiom eter:
500 km ; the total SSH accuracy (all
Resolve tropospheric correc tion
sc ales inc luded) shall be les s than 5.1
with 1.2 c m accurac y.
Hydrosphere Mapper Sc ienc e
cm (2) .
GPS:
O bjec tives: Measure m esoscale
Determine orbit with radial
ac tivity, including fronts , eddies, Within 30 km from the c oas t, the SSH
ac curacy of 2 cm .
and boundary currents; eddy
ac curacy at w avelengths shorter than
m ean-flow interactions, eddy
500 km shall be less than 4. 9 cm (3)
transports, and the role of eddies and the total SSH ac curacy shall be les s
in clim ate; phys ical-biological
than 5.3 c m (4) .
interactions and the role of eddies
in the carbon cyc le; coastal tides Wind speed m easurement s hall have an
and open ocean internal tides;
ac curacy of 2 m/s.
and coastal c urrents [B]
Global coverage of sea s urface height
m eas urem ents for ic e free oceans w ith
a repeat c ycle less than 25 days .
Sea Surface
Topography
Surface Topography
Sea
Monitor global m esoscale ac tivity
through the m easurement of sea
surfac e height (SSH) with a spatial
resolution of 1 km x 1 km w ith random
noise no greater than 1. 5 cm .
O rbit repeat periods shall be
between 10-25 days.
Non-s un-s ync hronous orbit is
required.
Fully c alibrated, validated s cience
data: Geolocated, calibrated
interferom eter s trip data of sea
Exact repeat ground trac ks with surfac e height on a per orbit bas is
cross -track s eparation less than on a 2 km grid near c oas tlines.
+/- 1 km.
Wind speed s trip data on a s imilar
grid. Both products with les s than
The attitude of the Ka-band
30 day latenc y.
interferom eter s hall be m aintained
steady (no yaw-s teering)
Q uick look data: Geolocated,
Fully c alibrated and validated
sc ienc e data are required w ithin
30 days. Q uick-look data w ith
les s quality are required within 1
day for coastal and other
operational applications .
Ka-band Interferometer: provide
Aliased periods of the eight leading tidal
above measurem ent acc uracy
components (M2, S2, K1, K2, P1, Q 1,
over a total s wath of [120] km.
N2, O 1) s hall be separated from one
another w ith maxim um period less than
one year.
3 year bas eline operation, w ith a 5 year 3 year reliability, with a 5 year
goal.
goal.
Apr24_06HM_pollardCharts_2.ppt
3 year bas eline m iss ion, with a 5
year goal.
partially c alibrated interferometer
strip data of s ea surface height on
a per orbit basis on a 2 km grid
near c oas tlines. Wind s peed strip
data on a sim ilar grid. Both
products with les s than 1 day
latenc y.
Advanced Altimeter Mission
NASA Requirements: Traceability Matrix
Bathymetry
Bathmetry
Sea Surface Topography
Cont. Sea Surface Topography
Ca tegoryScience Objectiv e s
Nadir Altimeter Science
O bjectives: Basin-scale ocean
circulation, heat transport, El
Nino/La Nina, sea level rise.
(2 of 2)
Scientific M ea sure me nt Requirements
Instrument F unctiona l Re quirements
M ission F unctiona l Re quirements
Le v el 2 Da ta Products
Measure ocean surface topography
covering at least -66 to +66 degrees in
latitude, w ith 3.4 cm accuracy at 6.2
Nadir Altimeter (Ku and C band):
km along-track resolution, w ith
2.6 cm height accuracy (1.6 cm
measurement drift less than 1mm/year.
Exact repeat ground tracks w ith
Ku noise, 2 cm sea-state bias, 0.5
cross-track separation less than
cm ionospheric error) w ith alongMeasurement products to continue the
+/- 1 km
track resolution of 6-7 km.
TO PEX/Poseidon, Jason, and
O STM/Jason-2 time series, although
different orbit inclinations and ground
tracks are acceptable.
3 year baseline operation, w ith a 5 year 3 year reliability, with a 5 year
goal.
goal.
3 year baseline mission, with a 5
year goal.
Geolocated, calibrated strip height
data on a per orbit basis on a 6.2
km grid. Wind speed strip data
on a similar grid.
Products to have less than a 30
day latency.
Data to be cross-calibrated versus
O STM nadir altimeter at
associated crossover points.
Ka-band Interferom eter:
Height precision (uncorrelated
The mission orbit design should
Measurement of East-West & NorthBathymetry Science O bjectives
:
random error) at 1km postings of include all orbit shifts required to
South
sea
surface
slope
to
1
microImprove understanding of marine
1.5 cm. Systematic error
get full ocean coverage over the
gravity field & global bathymetry radian over scales of 6-8 km.
contribution smaller than 1 micro-mission lifetime.
at (1) scales sufficient to resolve
radian over scales of 6-8 km
roughness that drives ocean
(residual slopes after calibration)
Global gravity & bathymetry maps
mixing, internal wave generation,
Global coverage between +/- 66 at 6-8 km resolution.
and tidal generation; and (2) to
Averaging of mesoscales signals degrees latitude with no spatial
determine the heights of
gaps.
seamounts accurately enough for Measurement of sea surface slope with requires at least 1 year data
100% coverage betw een +/- 66
collection for each point. Full
navigation and habitat
A mission lifetime of at least 2
degrees latitude.
coverage requires instrument
considerations [C].
years is required to average ocean
lifetime of at least two years.
mesoscale signal contamination.
Apr24_06HM_pollardCharts_2.ppt
References:
1. 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
2. The WatER Mission, www.geology.ohio-state.edu/water
3. 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
4. ABYSS-Lite: A radar altimeter for bathymetry, geodesy and mesoscale oceanography, Smith et. al. 2005
5. Altimetric BathmetrY from Surface Slopes, A Proposal in response to NASA AO01-OES-01, July 20, 2001, Principal Investigator: Dr. Walter H. F. Smith
Advanced Altimeter Mission
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
Advanced Altimeter Mission
NPOESS Requirements
Source: NPOESS Integrated Operational Requirements Document-II, January 2002
Advanced Altimeter Mission
NPOESS Requirements
Source: NPOESS Integrated Operational Requirements Document-II, January 2002
Advanced Altimeter Mission
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
Advanced Altimeter Mission
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 m^2 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
Ref: Francois Rogez (JPL) this study
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.
Advanced Altimeter Mission
Key Instrument Performance Parameters:
Ka-Band Interferometer Performance Summary
10-
4/18/06
Ref: Louise Veilleux Advanced Altimeter Mission Study, (JPL) April 2006
Advanced Altimeter Mission
Key Instrument Performance Parameters:
Ku & C-Band Altimeter & Radiometer Summary
10-
4/18/06
Ref: Louise Veilleux Advanced Altimeter Mission Study, (JPL) April 2006
Advanced Altimeter Mission
Science Measurement Requirements
• Continues the TOPEX/Jason/OSTM record while adding new capabilities
Measurement
Oceanography
M eas ure oc ean s urfac e topography between +/- 6 6 deg lat., with 3 .4 c m
ac c urac y, 6 .2 km res olution, drift < 1 mm/yr.
C ontinue T O P E X/P os eidon, J as on and O S T M time s eries
3 year mis s ion lifetime, with 5 - year goal
A void tidal alias ing
M onitor global mes os c ale ac tivity with 1 x1 km s patial res olution
Within 3 0 km of c oas t, meas ure S S H with 5 c m ac c urac y
G lobal c overage of S S H for ic e-free oc eans at intervals < 2 5 days
OSTM
Adv . Alt.
Y es
Y es
Y es
Y es
Y es
Y es
Y es
Y es
Y es
Y es
Y es
Bathy metry
M eas urement of E - W and N - S s ea s urfac e s lopes to 1 mic ro- radian over 6 8 km
M eas urement of s ea s urfac e s lope with 1 0 0 % c overage between +/- 6 6
deg lat.
Y es , in 3 years
Y es , in 3 years
Cry osphere
C entimeter ac c urac y topographic meas urements
A dequate s patial s ampling
Y es
Y es
Y es , exc ept for the
northernmos t part of
G reenland and the A ntarc tic
interior
Surface Water Hydrology
G lobal monitoring of water s torage c hanges
River dis c harge rates
L oc al River S lope
A dequate s patial s ampling
A dequate temporal s ampling
Floodplain topography
O nly larges t rivers
and lakes
Y es
Y es
Y es
Y es
Y es
For low relief topography
Ecology
C arbon fluxes at air-water boundaries
Y es
Advanced Altimeter Mission
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 standalone 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 (Jason2), need a Phase A start in 2007
==> Decision point shortly after release of decadal survey