The Geodetic Reference Antenna in Space (GRASP): A Mission to Enhance the Terrestrial Reference Frame

Transcription

1 The Geodetic Reference Antenna in Space (GRASP): A Mission to Enhance the Terrestrial Reference Frame Yoaz Bar-Sever, R. Steven Nerem, and the GRASP Team

2 The Most Complete Geodesy Mission Collocate all the geodetic technique on a supremely calibrated satellite Use as reference for all GNSS antennas (space and ground) Determine ground collocation at arbitrary baselines GRASP enhances science from past and future Earth science missions; ~30 year impact from a 3 year mission YEB, July

3 White records) YEB, July 2012 Key Science Goals Meet GGOS goals for the TRF: ~1 mm accuracy, 0.1 mm/yr stability Enable the accurate dissemination of the TRF with GNSS and DORIS to any location on Earth and low Earth orbit Measure the long-wavelength variability in the Earth gravity field that are either not observed (degree 1) or poorly observed (J 2 ) by GRACE Reinterpret satellite altimetry and tide gauge records to determine global mean sea level rise relative to the GRASP-based TRF how is sea level accelerating Reinterpret satellite ICESat and GRACE data records to determine ice mass loss relative to the GRASP-based TRF how is ice mass loss accelerating TRF errors readily manifest as spurious sea level rise accelerations Left: ITRF2005 (based on Church and White, 2011) Right: ITRF2000 (simulated into the Church and Sea Level (mm) TIDE GAUGE ALTIMETER RATE = 3.2 mm/yr Sea Level (mm) RATE = 1.5 mm/yr RATE = 2.0 mm/yr Acceleration = mm/yr 2 Acceleration = mm/yr Year Year TIDE GAUGE ALTIMETER RATE = 2.9 mm/yr

4 PI: S. Nerem Science Team: Altamimi Bar-Sever Biancale Chambers Gross Haines Lemoine Ma Murphy Pavlis Petrachenko Ries Schuh Schutz Wahr Willis R. Steven Nerem, Yoaz Bar-Sever, and the GRASP Submitted: Sep 29, 2011

5 YEB, July 2012 GPS Nadir (+Z) Phase Center Offsets

6 GLONASS Nadir Phase Center Offsets From Schmid et al., 2006 YEB, July

7 Legacy (Block IIA) Antennas Total Variation Relative to S/C Center of Mass Phase Variation (mm) BLOCK PHASE (LC) IIA SVN23 SVN24 SVN25 SVN26 SVN27 SVN30 SVN32 SVN33 SVN34 SVN35 SVN36 SVN38 SVN39 SVN40 Group Delay Variation (mm) BLOCK PSEUDORANGE IIA (PC) SVN23 SVN24 SVN25 SVN26 SVN27 SVN30 SVN32 SVN33 SVN34 SVN35 SVN36 SVN38 SVN39 SVN YEB, July 2012 Beam Angle (deg.) Beam Angle (deg.) Good consistency among individual PRNs for both phase and group delay LC map consistent with a spherical waveform with offset R: R (1 cos el); PC is not consistent with a spherical waveform December 17, 2010 Fall 2010 AGU Meeting BH- 7

8 Modernized (Block IIR-M) Antennas Total Variation Relative to S/C Center of Mass 80 PHASE BLOCK (LC) IIR-M 800 PSEUDORANGE BLOCK IIR-M (PC) Phase Variation (mm) SVN53 SVN52 SVN58 SVN55 SVN57 SVN48 Group Delay Variation (mm) SVN53 SVN52 SVN58 SVN55 SVN57 SVN Beam Angle (deg.) Beam Angle (deg.) Significant inter-spacecraft discrepancies for group delay (right) Similar-sized discrepancies observed for Legacy Block IIR (IIR-A) and IIR-B Neither phase nor group delay maps are consistent with a spherical waveform YEB, July 2012 December 17, 2010 Fall 2010 AGU Meeting BH- 8

9 Site where two or more instruments are operating Surveyed in three dimensions, using classical or GPS geodesy Ground Site (DX, Ties Between Differential coordinates DY, DZ)Techniques are available DX(GPS,VLBI) = XVLBI - XGPS SLR/LLR VLBI DORIS GNSS JPL, Pasadena, USA July 28, 2011 YEB, July /22/

10 The GRASP Spacecraft Orbit: 850x1350 Sun-synch Collocate sensors and CM to 1 mm 1 mm orbit determination 3 years lifetime GNSS Payload Antenna GNSS/DORIS Payload Electronics Star 6B De-orbit SRM 1.15 m 2 Solar Panel LRA Payload DORIS Antenna VLBI Payload Antennas VLBI Payload Electronics YEB, July 2012

11 YEB, July 2012 Novel Instruments on GRASP DORIS: New receiver capability incorporated into the JPL s TriG GNSS receiver (next generation BlackJack, with GPS, GLONASS, and Galileo all-in-view capability) DORIS phase measurements from up to 7 beacons Common time tags with GNSS measurements CNES already provided ICD; may ultimately contribute the standard DORIS receiver VLBI Tone Transmitter (VTT): A new instrument with heritage in several GRAIL subsystems Transmit power ~10 mw per band < 154 db (W/m 2/4 khz) at S-band Signal is compliant with NTIA < 150 db (W/m 2/4 khz) at X-band S-Band Tones X-Band Tones regulations while compatible with both present-day VLBI and VLBI2010 High precision ionospheric-free observables (1-σ, 1-sec) Ø 0.2 mm pseudorange (1 sec) Ø 0.01 mm phase (1 sec) JPL will write ground software to extract Level-1 (phase and pseudorange) observables from the broadband VLBI data; publish in RINEX-like format 2200 MHz 2290 MHz 8025 MHz 8400 MHz

12 Next Step: Looking for Partnerships We have a well-reviewed, complete mission concept We have a very strong and broad support from the geodetic community We have a broad base international scientific and technical leadership We aim to unify and calibrate all GNSS to enhance science interoperability We have an open data policy We are soliciting partnerships with agencies that are able to provide cost sharing or in-kind services, for example: Launch services Payload components Bus Ground system Estimated total mission cost: $100M over 6 years. YEB, July