Agenda for WATER HM/SWOT Meeting

CNES HQ, Paris

1 February 2008

Click Here for PDF version of Agenda  (agenda draft date: February 1, 2008)

Click here for a post-meeting summary of discussions (MSWord Version)

Start at 9:00 am, 1 hour Lunch break, end ~5:30 pm

9:00 - 9:10:  Welcome, Meeting Goals

            Nelly Mognard

 

9:10 - 10:00: Updates

            CNES Programmatic Status and updates

                        Pascale Ultré-Guérard

            NASA/JPL updates

                        Eric Lindstrom, Tony Freeman, Jim Graf

            IIP WATER HM Proposal

                        Lee Fu  (Ernesto Rodriguez)

            Results of Washington D.C. Meeting October 29th & 30th, 2007

                        Doug Alsdorf

 

10:00 - 11:45: Risk Reduction Studies

Discussion led by Ernesto Rodriguez, Bruno Cugny

            -  Discussion of the document describing the risk-reduction studies

            -  Plan to coordinate the NASA funded studies with those of CNES

 

11:45 – 12:15: Division of Technology Amongst Partners

            Discussion led by Ernesto Rodriguez, Bruno Cugny, Tony Freeman

            -  Mission sharing between NASA and CNES

            -  ITAR controls:  technology and potential sharing arrangements.

            -  Technology sharing to lower overall mission costs.

 

12:15 – 13:15:  Lunch

 

13:15 – 15:15:  Science Questions Discussions

            Hydrology and oceanography science questions

                        Doug Alsdorf, (with some slides by Lee Fu), Pierre-Yves Le Traon, Alix Lombard, Jacques Verron

            Coastal zone questions          

                        Lee Fu (Yves Menard), Florent Lyard, Pierre de Mey

Hydrology “Virtual Mission” updates

                        Doug Alsdorf, Sylvain Biancamaria, Dennis Lettenmaier, Aaron Boone

            Wording and Prioritization of the Science Questions

Discussion led by Doug Alsdorf, Lee Fu, Yves Menard, Nelly Mognard

            Applications of WATER HM to hydrology and oceanography

                        Dennis Lettenmaier

 

15:15 – 15:30: Break

 

15:30 – 16:30: Mission Document

 Discussion led by Anny Cazenave and Nelly Mognard

 

16:30 – 17:30: Miscellaneous, Open Forum

            Doug Alsdorf, Lee Fu, Yves Menard, Nelly Mognard

            -  Oceanography Workshops, Ocean Sciences ASLO meeting, Future “Town Halls”

Agenda Details:

Welcome, Meeting goals (10 minutes): Nelly Mognard

1.     Updates (50 minutes):

a.  CNES HQ update Pascale Ultré-Guérard.  CNES continues to strongly endorse WATER HM as a key earth science mission.

b.  NASA HQ and JPL discussions Eric Lindstrom, Tony Freeman, Jim Graf. Ongoing discussions regarding the future of WATER HM have focused on risk reduction studies which are designed to allow the SWG to formulate the mission requirements (e.g., science questions, technology constraints, costs, launch, platform, etc.).  These discussions encourage the participation of CNES, JPL, and NASA with an expectation of modest funds from NASA HQ and JPL throughout 2008 (funding of ~$0.5M to $1.0M).

c.  IIP WATER HM Proposal Lee Fu.  JPL submitted a proposal to NASA’s IIP call to reduce risks related to the mission.

d.  Results of Washington D.C. Meeting October 29th & 30th, 2007: Doug Alsdorf.  The meeting summary is appended below and should be used for reference.  The meeting was not able to conclusively solve the key issues related to the science questions and risk reduction studies because the Air France strike limited participation.  We will use this CNES meeting to finalize the plans for prioritizing the science questions and ensuring that risk reduction studies are well formulated and timed to finish so that the mission is ready for the next step.

2.     Risk Reduction Studies (1.75 hours): Ernesto Rodriguez, Bruno Cugny

a.  We have already circulated a 5-page document describing these risk-reduction studies and we will further discuss these during the meeting.  This document is also appended below.  Ernesto Rodriguez

b.  We need to work on a plan that will coordinate the NASA funded studies with those of CNES.

c.  Oceanography Workshops: 1. Coastal altimetry (Feb 5-7); 2. Meso- and sub-mesoscale processes (tentatively April); 3. Coastal and internal tides (TBD).  The first one will be finalized in a couple of weeks (Ted Strub and Laury Miller are the leads, jointly funded by NOAA and NASA).  The second one is being planned (Lee Fu and Raffaele Ferarri are the leads, NASA funded).  The third one is being considered by Richard Ray who will take the lead.  Lee Fu

3.     Division of Technology Amongst Partners (0.5 hours) Ernesto Rodriguez, Bruno Cugny, Tony Freeman

a.  Launch vehicle costs in the U.S. are on the order of ~$100M whereas costs are much lower for non-U.S. rockets.  Thus, one goal of the technology sharing is to lower overall mission costs.

b.  ITAR controls will restrict some aspects of the technology and potential sharing arrangements.  During the development of the WatER proposal to ESA, some of these details were discussed.

c.  NASA HQ has made it clear that sharing missions is a priority (e.g., Alan Stern presentation at Fall 2007 AGU).

 

4.     Science Questions (2.0 hours):

a.  The Washington D.C. meeting Doug Alsdorf, Lee Fu. The meeting resulted in an articulation of some science questions and identification of the topmost hydrology question and topmost oceanography question.  The wording of these questions is important because these drive the risk reduction studies and hence the mission design.  For example, storage changes in lakes, reservoirs, and wetlands are straightforward to measure whereas discharge in rivers is more complex requiring assessment of the space and time sampling via data assimilation.  See meeting summary below for more details.

b.  Coastal Zone Questions: Lee Fu, Pierre De Mey, Florent Lyard. Presentation by Pierre de Mey, “Model errors in coastal regions and the relevance to the SWOT mission to significantly constrain the coastal ocean mesoscale and coastal current variability”

c.  Hydrology “Virtual Mission” updates Doug Alsdorf, Nelly Mognard, Dennis Lettenmaier, Aaron Boone

d.  Wording and Prioritization of the Science Questions: Discussion led by Doug Alsdorf, Lee Fu, Yves Menard, Nelly Mognard

e.  Applications of WATER HM to hydrology and oceanography: Dennis Lettenmaier

5.     Mission Document for CNES (1 hour): Anny Cazenave, Nelly Mognard

a.  CNES would like to have a ~50 page document characterizing the mission and the studies needed to ensure that we are ready to move into the next mission phase.  An outline of this document is appended below.

b.  We need to discuss the content of this document and its authors, responsible for making certain we meet the CNES deadlines.

6.     Miscellaneous, Open Forum (1 hour): Doug Alsdorf, Lee Fu, Yves Menard, Nelly Mognard

a.  Ocean Sciences ASLO meeting, Orlando Florida, March 5, 2008

b.  Future Town Halls to ensure community buy-in

c.  Doug has helped serve as a conduit for emails describing the risk reduction studies, but I want to make certain that our technology members are fully aware of and contribute to the discussions.  Hopefully we can designate a knowledgeable engineer or two who would be willing to lead these discussions.  An outgrowth of the CNES mission document might also be designated leaders for other aspects of the mission.

d.  Mission web page(s): Do we need a forum section where participants can exchange their thoughts or is email sufficient?

e.  Mission names: Several names have been affiliated with the mission including the following.  The suggestion is to adopt SWOT as the official name.

                       i.    WATER HM: This is too cumbersome and needs shortening.  WATER would be better but may have some negative connotations in non-english languages.

                     ii.    Hydrosphere Mapper: Is too all encompassing of the water cycle, i.e., KaRIN will not map rainfall, evaporation, soil moisture, snow, ice, or groundwater which are all part of the hydrosphere.

                   iii.    Jason or similar first-names: While Jason was good because it linked to the Argo floats, I am reluctant to confuse wide-swath with conventional altimetry.  Perhaps there is a name, but I can't think of a first name that would fit wide-swath.

                    iv.    H2O: Hydrology and Oceanography Observatory (one H, two O's).  This sounds too much like a chemistry mission.

                      v.    SWOT: It is good to keep the traceability with the Decadal Survey and that would well-serve the U.S. community. For example, the recently passed U.S. Federal budget uses SWOT. Given that CNES has also used this name in their correspondence, it appears that they have also accepted SWOT.  The main negatives to this name are that it sounds like we are trying to hit something and that the acronym has no obvious meaning, especially with respect to hydrology or oceanography.  On the other hand, I'm guessing that the acronym has no strange meanings in non-english languages?

 

 

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Meeting Location Information

CNES Headquarters

Centre national d'études spatiales
2 place Maurice Quentin
75 039 PARIS CEDEX 01
FRANCE
Tel : 33 (0)1.44.76.75.00
Fax : 33 (0)1.44.76.76.76

CNES HQ is located near the famous Pont Neuf, Louvre, and Ile de la Cite.  The Metro system in Paris is outstanding and I think easy to use.  We are working on finding hotels, but you should feel free to find one yourself, but understand that Paris hotel rooms are very small.  Instead, enjoy the city!

I recommend taking the train from CDG into Paris: The rapid RER train service links Charles de Gaulle Airport with central Paris . Trains run every 15 minutes (eight minutes in peak periods) and the journey takes approximately 35 minutes. Line B runs from the TGV station at Terminal 2 to Gare du Nord, Châtelet-les-Halles (les Halles is next to CNES HQ), Saint-Michel and Denfert-Rochereau, with connections to the metro.

 

 

 

 

 

Invitees and Attendance (as of January 29, 2008)

 

Name

Email

Will Attend

Attending

Not Atttending

1

Aaron Boone

aaron.boone@meteo.fr

Y

1

 

2

Alain Mallet

alain.mallet@cnes.fr

Y

1

 

3

Alix Lombard

alix.lombard@legos.obs-mip.fr

Y

1

 

4

Anny Cazenave

anny.cazenave@cnes.fr

Y

1

 

5

Bruno Cugny

bruno.cugny@cnes.fr

Y

1

 

6

Bruno Lazard

bruno.lazard@cnes.fr

Y

1

 

7

C.K. Shum

ckshum@osu.edu

N

 

1

8

Dennis Lettenmaier

dennisl@u.washington.edu

Y

1

 

9

Detlef Stammer

detlef.stammer@t-online.de

 

 

 

10

Doug Alsdorf

alsdorf.1@osu.edu

Y

1

 

11

Dudley Chelton

chelton@coas.oregonstate.edu

N

 

1

12

Eric Dombrowsky

eric.dombrowsky@mercator-ocean.fr

Y

1

 

13

Eric Lindstrom

eric.j.lindstrom@nasa.gov

Y

1

 

14

Eric Thouvenot

Eric.Thouvenot@cnes.fr

Y

1

 

15

Ernesto Rodriguez

ernesto.rodriguez@jpl.nasa.gov

Y

1

 

16

Florent Lyard

florent.lyard@cnes.fr

Y

1

 

17

Gregg Jacobs

Gregg.Jacobs@nrlssc.navy.mil

Y

1

 

18

Herve Jeanjean

herve.jeanjean@cnes.fr

Y

1

 

19

Jacques Verron

jacques.verron@hmg.inpg.fr

Y

1

 

20

Jared Entin

jared.k.entin@nasa.gov

N

 

1

21

Jim Graf

James.E.Graf@jpl.nasa.gov

Y

1

 

22

Juliette Lambin

juliette.lambin@cnes.fr

Y

1

 

23

Larry Smith

lsmith@geog.ucla.edu

N

 

1

24

Lee-Lueng Fu

llf@jpl.nasa.gov

N

 

1

25

Nelly Mognard

nelly.mognard@cnes.fr

Y

1

 

26

Parag Vaze

pvaze@jpl.nasa.gov

 

 

 

27

Pascale Ultré-Guérard

 

Y

1

 

28

Paul Bates

paul.bates@bristol.ac.uk

Y

1

 

29

Pierre de Mey

pierre.de-mey@cnes.fr

Y

1

 

30

Pierre-Yves Le Traon

pierre.yves.le.traon@ifremer.fr

Y

1

 

31

Richard Ray

ray@nemo.gsfc.nasa.gov

N

 

1

32

Rosemary Morrow

Rosemary.Morrow@cnes.fr

N

 

1

33

Sophie Coutin-Faye

sophie.coutin-faye@cnes.fr

Y

1

 

34

Steve Nerem

nerem@colorado.edu

 

 

 

35

Sylvain Biancamaria

SYLVAIN.BIANCAMARIA@legos.obs-mip.fr

Y

1

 

36

Ted Strub

tstrub@coas.oregonstate.edu

N

 

1

37

Tony Freeman

anthony.freeman@jpl.nasa.gov

Y

1

 

38

Yi Chao

Yi.Chao@jpl.nasa.gov

N

 

1

39

Yves Menard

Yves.Menard@cnes.fr

N

 

1

 

 

 

 

26

10

 
Summary of:

Inaugural Meeting of the WATER HM Science Working Group

October 29th and 30th, 2007 in Washington D.C.

 

Your edits are welcomed. Date of this document is November 1, 2007; updated November 25, 2007

Link to Meeting Agenda and Presentations:

http://bprc.osu.edu/water/Meetings_WATERHM/FirstMeetingSWG_Fall2007/

 

While the Air France strike forced people to remain in France, our meeting still brought together a group of people from France, Germany, the U.K., and the U.S. (attendance is listed below). No official decisions were made, but recommendations were developed and are presented in this document for further discussion. The following is a summary of ideas developed and recommendations made during the meeting.  I hope to develop a more extensive write-up of the meeting.  -- Doug

1.     Phase A: The SWG should request that CNES and NASA HQ communicate regarding the need to keep WATER HM moving forward. CNES would like to move into Phase A studies in March 2008 whereas NASA HQ may not have the funds to support Phase A studies. Continued dialogue between Mike Freilich, Pascal Ultre-Guerard, Eric Thouvenot, and the WATER HM SWG is needed.

2.     Meetings: The inability of the hotel to supply effective telecom communication limited the interactions with those unable to attend the meeting. Follow-up meeting(s) including video-conferencing between JPL and CNES as well as face-to-face meetings are needed over the next one to three months.  Furthermore, given the lack of full SWG participation, it may not be appropriate to call the October 29th and 30th meeting the “inaugural” meeting.

3.     Mike Freilich indicated that he will closely follow the recommendations of the NRC Decadal Survey (DS) not only because of the scientific merits but also because the U.S. government relies heavily upon the recommendations of decadal surveys.

a.      He would like for the SWG to “close the loop” between the DS and the oceanographic and hydrologic communities, i.e., to ensure that the respective communities confirm that the mission capabilities address the important science questions. This is largely already done for WATER HM, especially given all of our previous two years work. 

b.     He would like for us to continue to be “firm, objective, persuasive, and sustained advocates” of WATER HM because, while the DS may have justified the mission, the DS did not make the arguments to the necessary depth. If we fail to keep the momentum, it is possible to slip in time, but, on the other hand, activities are unlikely to move the mission forward in time ahead of Phase 1 DS missions.

c.      Before Mike Freilich arrived at our meeting, I indicated that both houses of Congress have appropriated between $60M and $100M for NASA’s Earth Science Division. Freilich reiterated the above point. [Editorial note: A reading of the House bill, page 112, indicates that these moneys are for the first seven DS missions, including WATER HM and that these funds are intended to allow Phase A and pre-Phase A studies.  It is has been suggested in the national media that the overall funding bill will likely be vetoed by the President].

d.     WATER HM will not be an ESSP mission. ESSP is for missions outside of the DS.

e.      Jason-3 appears to becoming less firm, not more firm.

4.     Science questions are prioritized but are not as well articulated as needed. Societal questions should not drive the mission and, instead, should be a direct result of the science questions.

a.      WATER HM will produce data that should transform hydrology, much like Topex/Poseidon did for oceanography nearly 20 years ago.

b.     The topmost hydrology question should either include both storage changes and discharge, or focus on just storage changes. The implications of the word “prediction” imply something about the future whereas we should say “estimate”, thus indicate an immediate result of WATER HM.

c.      The topmost oceanographic question is focused on eddy kinetic energy (i.e., measuring EKE at the fine spatial-scale necessary to understand the energy dissipation). Measurements of sea-surface heights in coastal zones are also a priority, especially given that conventional altimetry significantly under-samples the coasts. The question dealing with hurricanes is not well worded and should probably not emphasize hurricanes, instead place an emphasis on air-sea interactions.

5.     Risk reduction studies are needed to further refine the mission and keep it on track for a launch in the 2013-2016 timeframe indicated by the DS.  Studies include:

a.      WSOA was not designed as a Ka-band SAR system, thus the extensive JPL studies conducted for WSOA need to be expanded to include Ka-band and the ability to produce a synthetic aperture.

b.     Given that all early DS missions will produce large amounts of data, it is possible that additional downlink capacity will be available by launch. Nevertheless, on-board processing to reduce data volumes might be required. Such processing needs to be prototyped.

c.      Corrections for the wet and dry troposphere are needed. Regarding radiometers, what are their power requirements and what are the risks associated with newly developed ones? Conventional radiometers are viable for WATER HM over the oceans, thus what are the alternatives to advanced radiometers for making corrections over coastal and land areas?

d.     The Ka-band radar studies over three Ohio water bodies were useful for demonstrating that KaRIN will record off-nadir returns. It would be beneficial to have a more extensive study of the surface conditions, wind speeds, and resultant backscatter strength and signal correlation. Perhaps adding beamwidth and pulse size to the study would help delineate the implications of small “flat patches” along river surfaces.

6.     Mission design studies, like the risk reduction studies, will help delineate the power, accuracy, and sampling.

a.      The orbit should be within an inclination of 66 to 90 degrees, an altitude of ~800 to ~1000 km, and non-sun-synchronous. A French development, Platform 2012, is capable of handling the expected power requirements, articulated solar panels, and instruments for WATER HM. There is an overwhelming majority in favor of a non-sun-synchronous orbit. Thus any effort to move away from the general orbit defined above will require a study that clearly defines the benefits of an alternative orbit.

b.     The hydrology virtual mission will demonstrate the time and space trade-offs (orbital sampling) for deriving water storage changes and estimating discharge. Given that every watershed around the world will be sampled every orbital repeat cycle (and most likely every half repeat cycle), data assimilation is an ideal tool to define the derived storage change and discharge accuracies and errors. Similar coastal zone and oceanographic virtual missions should also be considered. These will not alter the science questions, rather will help to carefully define the expected gains in science.

7.     A report of the SWG is needed to enable the mission to move into Phase A studies. The report will define the motivating science questions, make a preliminary mission design, and establish a mission timeline. The report will take about a year to complete. It includes the risk reduction and mission definition studies. A preliminary version of this report could be distributed in February 2008 to enable a “pre-Phase A” description of WATER HM.

 

Meeting Attendees: Anthony Freeman, Bruno Lazard, C.K. Shum, Dani Esteban Fernandez, Delwyn Moller, Dennis Lettenmaier, Detlef Stammer, Diane Evans, Doug Alsdorf, Eric Lindstrom, Ernesto Rodriguez, Gregg Jacobs, Jared Entin, John Melack, Kostas Andreadis, Larry Smith, Lee-Lueng Fu, Mike Durand, Paul Bates, Richard Ray, Shannon Brown, Steve Nerem, Ted Strub, Yi Chao

 

Invited but unable to attend: Aaron Boone, Anny Cazenave, Bruno Cugny, Dudley Chelton, Eric Dombrowsky, Eric Thouvenot, Eric Wood, Estelle Obligis, Florent Lyard, Herve Jeanjean, Jacques Verron, Jay Famiglietti, Nelly Mognard, Pascale Ultre-Guerard, Pierre-Yves Le Traon, Pierre de May, Rosemary Morrow, Yves Menard

 

 

 

 


Risk Reduction Studies for WATER HM

Document Date: 21 Nov 07

Contacts

Doug Alsdorf (alsdorf.1@osu.edu)

Ernesto Rodriguez (ernesto.rodriguez@jpl.nasa.gov)

Lee-Lueng Fu (llf@jpl.nasa.gov)

 

We have been encouraged by NASA HQ and JPL to create a prioritized list of studies for defining the WATER HM mission.  These studies will focus on the goal of the WATER HM Science Working Group (SWG), i.e., to formulate the mission’s science goals and requirements and to conduct a mission definition study leading to an optimal preliminary design of the mission given science requirements and technology and cost constraints.

 

During the SWG meeting of October 29-30, 2007, we discussed a number of risk reduction studies and suggested a priority ordering.  Those studies and their prioritization are briefly presented below.  We very much would like to have your comments and thoughts on this list.  We want to ensure that our oceanography and hydrology communities are in agreement regarding the needed studies and the approach we should take toward completing the studies.

 

Please feel free to contact Lee Fu or Doug Alsdorf with your thoughts.  We need to deliver these ideas to NASA HQ and JPL no later than the first week of December 2007.  NASA HQ and JPL are both looking at the possibility of funding studies that would start immediately and be completed within a year.

 

The following studies are grouped in stages to allow collaborative efforts between oceanography, hydrology, and technology teams. Integration and feedback between the teams is needed to reduce mission risks.

First Stage: Year One

The following are needed by the end of the first stage; (1) the basic science requirements should be identified, (2) a process to ensure that the details of the science-cost trade-offs is in place and working toward solutions, and (3) the technology needed to meet the science requirements is defined, and the mission requirements finalized. These first year priorities are tasks leading to the SWG report, which will summarize the science rationales, science requirements, and preliminary instrument and mission design. The SWG report will form the basis for defining a set of mission Level 1 science requirements, to be used by the mission definition team as a basis for developing a mission and instrument design.

Oceanography Priorities:

1. Define the science scope and significance for the exploration of the sub-mesoscale processes and measurement requirements.

2. Review the coastal tide models and develop a plan for improvement; development of internal tide models and predictions.

3. Review the state of the art in modeling mesoscale atmospheric water vapor, as well as improved algorithms for conventional radiometer water-vapor retrieval for coastal ocean applications.

4. Develop science questions in mesoscale air-sea interaction processes.

These priorities will be accomplished by working groups holding workshops focused on each priority. The workshop recommendations will be implemented in Stage 2. Operating these workshops will take one-year.

Hydrology Priority:

1. Define the spatial and temporal sampling, spatial resolution, and height accuracies needed to address the main hydrology science question which is focused on the terrestrial surface water balance.  Essentially, this is the virtual mission study.  However, the VM is a three-year project with emphasis on developing a method of estimating discharge. To meet a one-year time requirement, we should focus additional efforts on determining the time and space sampling and accuracies needed to understand storage changes (a simpler measurement compared to discharge).

This priority will be accomplished using existing data bases, showing the locations and spatial sizes of wetlands, lakes, and reservoirs, coupled with various orbit configurations to demonstrate the sampling strategies and their impact on measuring potential storage changes, globally.  This effort will take one-year.

Mission and Instrument Definition Priorities:

The priorities of the first year’s study will be to conduct a set of instrument and mission definition studies that will:

1.  Define an instrument suite capable of meeting the science measurement requirements produced by the science team activities described above.

2.  Derive an expected instrument performance error budget for each of the science applications defined by the science team.

3.  Identify key technology drivers, and propose implementation solutions which can be accomplished in the timeframe of the development of the WATER HM mission and within its expected budget.

4.  Identify key mission risks and drivers to be addressed during the second year of the study.

 

The KaRIN instrument was designed to meet a set of hydrology requirements for WatER, an ESA proposed mission, using a 16-day repeat sun-synchronous orbit at 800 km orbit altitude. The mission was also to be implemented on a European Prima satellite bus, which is no longer under consideration for the WATER HM mission. The power, accuracy, data rate and data volume were designed to meet the constraints of the Prima platform and funding constraints imposed by ESA.

 

Since its conception, the requirements on the instrument suite have changed substantially. The orbit currently under consideration has a 21-day repeat at an altitude up to nearly 1000 km. The orbit is also non-sun-synchronous, which greatly increases the requirements on the power generation subsystem and the thermal environment under which the instruments must operate. In addition, the instrument suite must now be enhanced to accommodate a Jason-class nadir altimeter and a three (or more) frequency radiometer to meet the ocean science requirements. The addition of ocean data collection increases the total data which must be collected by a factor of about 2.5, requiring a complete re-examination of the data collection, processing, storage, and downlink strategies.

 

Finally, the ability to measure centimetric topography globally requires sensitive calibration procedures to remove the effects of spacecraft attitude, interferometric phase drift, and tropospheric delay effects. The ability to calibrate these effects is intrinsically tied to the orbital design, the design of the solar panels, and the attitude control system. These studies were conducted in the past for the Wide-Swath Ocean Altimeter (WSOA) instrument, which had a completely different orbit and operating environment.

 

In order to meet these mission and instrument definition priorities, we propose the following four focused tasks:

1.  Mission Orbital Design Space Definition: This task will take into account the space-time coverage and aliasing requirements defined by the SWG  and define a set of orbits meeting these requirements. This orbit space will be used in subsequent instrument and mission trade studies to define the optimal instrument and mission implementation.

2.  Mission and Instrument Definition Study: Given the results of the orbital design space study and a working set of Level 1 science requirements, this task will generate an instrument and mission design suitable for meeting the science requirements.  Specific issues to be addressed include:

a.  Definition of the key instrument parameters required to meet the desired science performance.

b.  Definition of the instrument design to a block diagram level, with the identification of key instrument components (e.g., Ka-band tube) and associated instrument mechanical configuration, mass, power, and data rate budgets. Identification of key critical technology risks and risk reduction plan.

c.  Definition of key spacecraft requirements with proposed implementation solutions. These studies are to include: (1) a design for the generation of the power required to operate the instruments in the desired orbit for continuous data collection; (2) a design for a data system capable of handling the large data volume to be generated by this mission. The study will include the examination of the feasibility of onboard data compression, the capabilities of solid state recorders, data downlink subsystems, and the number of ground stations required to support the mission. The SWG will be intrinsically involved in this phase of the study addressing critical issues such as which areas require high resolution coverage (e.g., how much of the coasts need to be covered at high resolutions; or how much of the land area is not of hydrologic interest), and what level of resolution is required for the compressed data. (3) Development of the expected attitude variability spectrum and the capability to monitor it. These studies explore the relationship between systematic error sources introduced by the spacecraft attitude control system (ACS), and the mast, antenna, and solar panel dynamics. It is a required input for deriving a mission error budget and defining requirements to be placed on spacecraft suppliers as part of the mission implementation process.

d.  Expected Deliverables: Mission and instrument definition documents suitable to be used as a basis for mission costs studies and mission and instrument requirement documents. Definition of key risk items and plans for year 2 activities.

3.  Instrument Error Budget and Calibration: The purpose of this task is to develop an integrated measurement error budget for the system defined by task 2. The error budget will consist of characterization of random errors due to system thermal and speckle noise, integrated sidelobe, quantization and processing noise. In addition, and more importantly, this study would examine the effects of long wavelength or systematic noise errors and their mitigation using suitable calibration schemes, to be developed as part of this task. The systematic instrument noise errors are due to unknown spacecraft roll motion or interferometric phase drift. Additional sources of long-wavelength errors are due to uncompensated wet-tropospheric delays. As part of this study, we will develop cross-over calibration techniques, as first proposed for the WSOA mission, and digital elevation model (DEM) calibration techniques for land calibration. Realistic error sources will be modeled using the results of the ACS study in task 2, and using the best available geophysical fields (ECMWF models, GPS inversions, and radiosonde data) to model the magnitude and space-time characteristics of the wet and dry tropospheric delay fields. Finally, the impact of the nadir altimeter system and different configurations of the radiometer will be assessed to establish the requirements on these complimentary instruments. The study will examine the calibration capabilities in three different regions: a. the deep ocean (an evolution of the WSOA calibration to the new orbit, swath and resolution); b. Coastal regions (not addressed by WSOA) and large inland water bodies; c. Rivers, wetlands, and small lakes. As part of this last task, the impact of vegetation on the error budget and the calibration will be assessed.  An error budget will also be derived for the measurement of floodplain topography over the lifetime of the mission.

4.  Experimental Data Collection: Recent experimental campaigns have collected river data that indicate that there may be fundamental limits to the spatial resolution and, potentially, some swath loss, especially if lower orbits (larger incidence angles) are utilized. These data collections were extremely limited, and therefore the impact on the mission performance cannot be fully assessed. We propose to use the same experimental radar system used to collect the first set of data to conduct additional data collections to better understand these limitations.

The studies identified above have concentrated on the interplay between the mission science requirements, the mission design, and the instrument performance. Due to the complicated optimization that is required to arrive at a suitable mission design within the technology and costs constraints, it is highly desirable that all of these studies be conducted concurrently, and that is the rationale for proposing them as an integrated first year study which defines the science goals and performance for the integrated mission.

In addition to these required end-to-end studies, we have identified a set of technology risk items which can be addressed by the NASA Earth Science and Technology Office (ESTO). These technology items are:

·       The KaRIN antenna implementation.

·       The onboard processor required to process the ocean data.

·       The high-frequency radiometer required to remove wet tropospheric errors in coastal regions and over large water bodies.

Given the detailed technical nature of these tasks, we will be submitting a proposal to ESTO as part of the latest Instrument Incubator Proposal (IIP) call as suitable candidates to be matured under the ESTO IIP process.

 

 

Second Stage: Year Two

The following are needed by the end of the second stage: (1) Named people who will eventually become the mission team – some of these people will have already worked on the risk reduction studies and thus developed a great familiarity with WATER HM. (2) Mission accommodation studies to identify suitable spacecraft and launch vehicles and detailed cost studies for the range of possible mission scenarios; (3) Definition of science data products at levels 2 and 3, and associated sizing of the algorithm development effort and the ground processing system. (4) Retiring critical risk items, as determined during the first year studies. (5) Development of suitable documents required for the Mission and System Readiness reviews to be held soon after the start of Phase A.  To ensure that WATER HM is prepared for Phase-A studies, these tasks need to be accomplished by the end of year two (i.e., one year after Stage 1).

Oceanography priorities:

1. Conduct numerical simulations of sub-mesoscale processes and refine science questions.

2. Improve coastal tide models and development of internal tide models.

3. Improve coastal altimeter data products and refine science questions.

4. Conduct investigations on mesoscale air-sea interaction and refine science questions.

These priorities are initiated during year one and will be completed during Stage 2.

Hydrology Priorities:

1.  Define the time and space sampling needed for estimating discharge.

Priority 1 is already funded by NASA’s Terrestrial Hydrology Program (i.e., the “Virtual Mission”), and thus is already ongoing. Significant portions of this discharge study will be completed and timed to support the mission definition studies. However the VM is focused on a small number of locations, presently defined as one 300 km reach along the Amazon River, another on the Ohio River, and a third in the Peace-Athabasca system of northern Canada. Characterization of other major river systems would be ideal, such as the Nile, Ganges-Brahmaputra, Ob and Lena, etc.

Mission and Instrument Studies:

1. Define bus and launch vehicle accommodation requirements.

2. Design the ground data system and mature key algorithms for the data processing system.

3. Address key risk items identified during the first year.

4. Develop a preliminary mission cost.

5. Develop system and mission design and associated documentation to a level consistent with a mission start at the end of the 2nd year tasks.

 

 

 

 


Suggested Outline of CNES Mission Document

 

Title: Wide-Swath Altimetric Measurement of Water Elevation on Earth

  1. Introduction
  2. Science questions

Oceanography --> Lee  Fu , Rosemary  Morrow , Yves  Ménard, Pierre de Mey ,..  

Hydrology --> Doug  Alsdorf , Nelly Mognard,.. 

Global sea level and water cycles --> Anny  Cazenave , ..

Geophysics --> Anny  Cazenave, Louis Geli,... 

        3.  Measurement of water elevation

Radar altimetry --> JPL, CNES

Radar interferometry --> JPL, CNES

Effects of ocean tides --> Florent Lyard ,... 

Effects of tropospheric water vapor --> JPL, CLS

Effects of rain --> Ernesto  Rodriguez ,..

        4.  A mission to map the water elevation on Earth

Science goals and requirements

Mission design issues

  • Orbit and sampling issues --> JPL, CNES ,  Virtual Missions --> 
  • Precision orbit determination -->  JPL, CNES
  • Spatial resolution --> JPL, CNES ,  Virtual Missions -->
  • Water vapor radiometer --> JPL, CLS
  • Data rate and downlink requirements --> JPL, CNES
  • Calibration and validation --> JPL, CNES

A mission configuration