NGGM ASSESSMENT STUDY Progress Meeting 3 TASI Torino

NGGM ASSESSMENT STUDY Progress Meeting 3 TAS-I, Torino, 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Agenda Page 2 9. 15 9. 30 11. 00 12. 00 13. 30 14. 30 16. 15 16. 30 Introduction and Agenda Task 2: Observing techniques WP 2120 Instrument Concepts TAS-I WP 2121 Measurement Technologies ONERA WP 2110 Observing Techniques DEOS [IAPG] Task 3: Mission analysis and attitude and orbit control concepts WP 2220 Attitude and Orbit Control Concepts TAS-I WP 2210 Mission Analysis TAS-I [DEIMOS] Task 5: Mission Architecture Outlines WP 2420: Mission Architecture DEOS [GIS] WP 2410: Architecture Definition and Trade-Off TAS-I Lunch break Task 4: Simulation Tool WP 2310 End-to-End Simulator Design and Implementation TAS-I WP 2320 Variable Gravity Model DEOS [IAPG] WP 2330 Backward Module DEOS Discussion, Planning Adjourn NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 3 WP 2110 Observing techniques (IAPG) T. Gruber, M. Murböck NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Prioritization of Science Requirements Page 4 From Chapter 8 of NGGM_SCI_1: • Primary focus on ice, continental water, ocean masses and solid Earth. • Highest rated signals to be observed are given in following table. Signals magnitudes, temporal & spatial resolution taken from science requirements analysis. • Translation of gravity potential to EWLT (equ. Water layer thickness): Description Spatial resolution Temporal resolution 1 Melting of ice sheets (with separation of GIA) 100 – 1000 km Seasonal – secular 2 Non-steric comp. of sealevel var. at seasonal and shorter time scales Global to basin level Interannual – secular 0. 1 mm/year (secular) 3 Ground water (, soil moisture and snow) at higher spatial scales 10 – 200 km Hourly – seasonal – secular 1 cm (seasonal) 10 – 200 km Subseasonal Assessment Study deformation 4 NGGMPost-seismic 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE Signal magnitude in geoid heights 0. 01 mm/year (secular) 1 mm (subseasonal) All rights reserved, 2010, Thales Alenia Space

Nominal Mission Profile Requirements Page 5 From science requirements prioritization one can derive nominal mission profile requirements: • Temporal resolution 1 month for complete cycle. • Sub-monthly sub-cycle is of high interest. • Mission lifetime 11 years for long term trends (solar cycle). • Inclination close to 90 degrees to observe polar areas. Science requirements are translated into maximum cumulative geoid errors (CGE) for the nominal mission profile and for monthly gravity field solutions. Secular signal magnitude requirements are translated into monthly gravity field requirements by applying a factor of 10. This is correct when assuming a reduction of errors for 11 years of monthly data when applying a linear trend estimations. NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Nominal Mission Profile Requirements Page 6 Cummulative geoid error requirements for monthly solutions: Wavelength SH degree 10000 km 1000 km 200 km 10 km 2 20 100 2000 10 mm CGE 3 1 mm 2 4 0. 1 mm 1 Signal 1 = Melting of ice sheets Signal 3 = Ground water variations Signal 2 = Non-steric sea level variations Signal 4 = Post-seismic deformation Restriction to more realistic requirements by limiting spatial resolution to be reached with a specific CGE. This leads to a compromise when taking into account only the green bars in the table above. The CGE requirements to be applied for simulations are defined as follows: NGGM Assessment Study 26 May 2010 SH degree 150 200 250 CGE [mm] 0. 1 1 10 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Simulations Summary Page 7 Requirements for the SST sensor and the accelerometer to meet the required CGE values (wn: white noise, cn: coloured noise). Every mission profile belonging to a grey box will not meet the requirements with the minimum noise levels. Satellite Separation [km] 50 wn SST ACC Altitude [km] NGGM Assessment Study 26 May 2010 100 cn wn 200 cn 300 wn cn 300 5, E-13 4, E-13 1, E-13 4, E-14 3, E-14 350 8, E-14 7, E-14 6, E-14 5, E-14 <1, E-14 400 2, E-14 <1, E-14 <1, E-14 450 <1, E-14 <1, E-14 500 <1, E-14 <1, E-14 550 <1, E-14 <1, E-14 600 <1, E-14 <1, E-14 300 2, E-11 8, E-12 4, E-11 9, E-12 7, E-11 3, E-11 9, E-11 5, E-11 350 6, E-12 3, E-12 2, E-11 6, E-12 3, E-11 2, E-11 400 2, E-12 8, E-13 3, E-12 2, E-12 5, E-12 3, E-12 6, E-12 5, E-12 450 <5, E-13 8, E-13 6, E-13 1, E-12 9, E-13 500 <5, E-13 <5, E-13 550 <5, E-13 <5, E-13 600 <5, E-13 INTERNAL THALES ALENIA SPACE <5, E-13 COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space <5, E-13

Page 8 Discussion items: - - representation science requirements (ice, hydrology, etc. ): e. g. global grids with locations were signals occur also “scaling” of requirements: spatial vs. temporal (e. g. long -wavelength hydrology at short periods, smaller features at longer periods) benefit of flying two pairs (ESA + NASA): orbit characteristics (repeat cycles, sub-cycles, etc. ) NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 9 WP 2420 Mission Architecture (GIS) T. Reubelt, N. Sneeuw NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Content Page 10 Quick-look-tool simulations - Comparison of formations (only for white noise) - GRACE-BENDER-configurations (2 GRACE-like pairs on different inclinations); coloured noise used - Mixed BENDER configurations (polar GRACE + another inclined formation); only for white noise ● (pseudo-) Quick-look tool formations works now for white noise on the level of range-accelerations. It is based on orbit computation (circular repeat orbits) and the solution of the Hill-equations. NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Formations (comparison) Page 11 GRACE (ρ = 75 km) PENDULUM (ρx = ρy = 62 km) CARTWHEEL (ρr = 50 km, ρx = 100 km equatorial radial) I = 90°, psd = 1 -10 m/s²/sqrt(Hz), T = 32 d, h = 335 km NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Formations (comparison) Page 12 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Formations (pendulums) Page 13 PENDULUM (ρx = ρy = 62 km, → α = 45°) PENDULUM (ρx = 71 km, ρy = 35. 5 km, → α = 67°) PENDULUM (ρx = 46 km, ρy = 92 km, →α = 23°) I = 90°, psd = 1 -10 m/s²/sqrt(Hz), T = 32 d, h = 335 km NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Formations (pendulums) Page 14 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Formations (cartwheels) Page 15 CARTWHEEL (ρr = 50 km, ρx = 100 km, equatorial radial) CARTWHEEL (ρr = 50 km, ρx = 100 km, polar radial) CARTWHEEL (ρr = 50 km, ρx = 100 km, radial at φ = 45°) I = 90°, psd = 1 -10 m/s²/sqrt(Hz), T = 32 d, h = 335 km NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Formations (cartwheels) Page 16 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Formations Page 17 Discussion/results - most accurate and homogeneous results for PENDULUMs are obtained for an yaw angle of α = 45° - most accurate and homogeneous results for CARTWHEELS are obtained if the CARTWHEEL is radial over equatorial regions; but also if it is radial over regions with φ = ± 45° - in general PENDULUMs and CARTWHEELs improve sensitivity and isotropy compared to GRACE-formations; similar accuracy for PENDULUM and CARTWHEEL NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

GRACE-BENDER for coloured noise Page 18 GRACE (polar), h = 335 km, T = 32 d GRACE (SSO) h = 348 km, T = 32 d GRACE (I = 63°) h = 352 km, T = 31 d ρ = 75 km, new reference noise NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

GRACE-BENDER for coloured noise Page 19 GRACE (polar), h = 335 km, T = 32 d GRACE-BENDER (polar + SSO) GRACE-BENDER (polar + I=63°) ρ = 75 km, new reference noise NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

GRACE-BENDER for coloured noise Page 20 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

GRACE-BENDER for coloured noise Page 21 Discussion/results - highest sensitivity and isotropy reached for the combination of a polar and a low-inclined (I = 63°) satellite pair NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

polar BENDER-constellations for white noise here: single pair SSO I = 63° Page 22 GRACE PENDULUM (left satellite is leading) PENDULUM (right satellite is leading) CARTWHEEL NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

BENDER-constellations for white noise polar + SSO polar + I=63° Page 23 polar GRACE + GRACE polar GRACE + PENDULUM (left s. Is leading) polar GRACE + PENDULUM (right s. Is leading) polar GRACE + CARTWHEEL NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

BENDER-constellations for white noise Page 24 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

BENDER-constellations for white noise Page 25 Discussion/results - combination of satellite pairs with different distribution of the formal errors seems to be most promising - It has to be taken care of at inclined PENDULUMs which satellite is the leading one - promising results by the combination of a polar GRACE with an inclined PENDULUM/CARTWHEEL, especially in case of SSO inclination; most promising seems to be the combination with a SSO-PENDULUM NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 26 WP 2320 Variable gravity model (IAPG) T. Gruber, M. Murböck NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Activities Page 27 Activities/results previous period: • Check of Greenland ice mass field for negative trend started. Original Greenland ice mass fields show expected negative trend. Activities planned: • Further check of pre-processing of Greenland ice mass fields in order to identify where positive trend occurred. • After finalization of pre-processing check and in case problem could be identified it is intended to reprocess fields for 1995 and 1996 first and to perform the re-combination of new hydrology fields and all other mass fields. • It is expected to finalize the 2 years by mid June in order to use them for numerical simulations. • Remaining period from 1997 to 2006 will be processed afterwards and a complete updated time variable gravity model shall be made available until MAR (mid July). NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 28 WP 2330 Backward module (DEOS) P. Visser, P. Ditmar, J. de Teixeira da Encarnacao NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 29 Orbital elements generated and provided for TAS forward E 2 E module: 1 in-line polar, 75 km baseline, 32/503 repeat, 4/7 -day sub-cycles 2 in-line Bender, 75 km baseline, 31/481 repeat, 63 O inclination 3 in-line SSO, 75 km baseline, 32/503 repeat, 4/7 -day sub-cycles 4 pendulum polar, 62/62 km baseline, 32/503 repeat, 4/7 -day subcycles 5 cartwheel polar, 50/100 km baseline, 32/503 repeat, 4/7 -day subcycles Following slides: tests with first week (Jan 3 -9, 1996) of data generated by TAS forward E 2 E module for scenario 1. NB: initial conditions from forward E 2 E simulator were shifted by 11 sec (UTC/GPS time difference) for backward E 2 E simulator! NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 30 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 31 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 32 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 33 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 34 Low-low Satellite-to-Satellite Tracking module NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 35 Gravity field retrieval experiments: • 1 week (3 -9 January 1996): observable signal is 50 x 50 hydrology • • • ll-SST range-rate, decimated to 1 observation per 20 s (range-rate reduces colored noise of ranges significantly) x, y, z position coordinates (pseudo GNSS) assessment of error sources: • observation noise (plus orbit errors) • attitude reconstruction errors • accelerometer noise NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 36 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 37 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Hydrological signal (equivalent water height) Page 38 Unsmoothed NGGM Assessment Study 26 May 2010 20 o-smoothed INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Temporal aliasing Page 39 Unsmoothed NGGM Assessment Study 26 May 2010 20 o-smoothed INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Acc+att+obs errors, 30 min pwl accelerations Page 40 Unsmoothed NGGM Assessment Study 26 May 2010 20 o-smoothed INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Page 41 Satellite Gravity Gradient module NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

1. Processing of data contaminated by Instrumental noise Page 42 • 30 -day data set (release 19/3/2010, 5 -day repeat orbit, orbit altitude ~ 312 km) • Maximum spherical harmonic degree: 99 • “Shaped noise” in gravity gradients (see next slide) • Considered components (per scenario): 1. 2. 3. 4. Vxx + Vyy + Vzz Vzz Vyy NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

SQRT-PSD of noise in gravity gradients Page 43 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Geoid height error per degree Page 44 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Error per coefficient (log scale) Page 45 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Geoid height error per order (degree 60) Page 46 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

2. Processing of (noise-free) data with mass transport signals Page 47 • Orbits and maximum degree are the same as before (release 19/3/2010, max SH degree 99) • 6 -hours time-varying gravity field models from the Mass Transport Project • Representing Atmospheric, Oceanic, Hydrologic, Icerelated and Solid earth-related (AOHIS) mass transport processes (without de-trending) • Considered components (per scenario): 1. Vzz 2. Vyy + Vzz • The difference between the recovered gravity field and the true mean field of the month (August 2004) is analyzed (the temporal aliasing effect) NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Geoid height difference per degree Page 48 NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Conclusions Page 49 • The absence of Vxx component has a minor effect on the added value of SGG data • The remaining gravity gradients (Vyy and Vzz) show a strong synergy effect (the absence of either of the two increases errors by an order of magnitude) • SGG data (Vyy+Vzz scenario) show a very isotropic sensitivity. In contrast, hl-SST data can cause errors that strongly depend on the spherical harmonic order. Thus, SGG data may have an added value (especially at nearly-sectorial orders) even if the total errorper-degree is relatively large. • The Vyy+Vzz greatly mitigates temporal aliasing, which is probably related to an isotropic sensitivity of observations in this case • Further analysis of the added value of SGG data is needed. NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space

Future outlook Page 50 • Analysis of newer simulated data sets • Taking attitude reconstruction noise into account • Contribution to a joint processing of SGG and ll-SST data NGGM Assessment Study 26 May 2010 INTERNAL THALES ALENIA SPACE COMMERCIAL IN CONFIDENCE All rights reserved, 2010, Thales Alenia Space