Reduced GEROS-ISS Mission

Transcription

1 educed GEOS-ISS Mission M. Martín-Neira 1, J. Hatton 1, M. Kern 1, J. Benito 2, A. Andrés-Beivide 2, S. Moreno 2,. Vilaseca 3, H. Fragner 4, A. Dielacher 4, J. Wickert 5, E. Cardellach 6 1 European Space Agency (Noordwijk, The Netherlands) 2 Airbus DS, Space Systems España (Madrid, Spain) 3 TYO Group Aerospace and Electronics (Barcelona, Spain) 4 UAG Space Austria (Vienna, Austria) 5 GeoForgsZentrum (Potsdam, Germany) 6 Institute of Space Studies (Barcelona, Spain)

2 GEOS-ISS: GNSS eflectometry, adio Occultation and Scatterometry on board the ISS GNSS+17, Ann Arbor (Michigan, USA), May /24

3 Background GEOS-ISS Phase A and Science (GACA) studies ended mid 2016 Payload was too expensive need for a Cost eduction Exercise Planned schedule (as per September 2016): CE Phase B Phase C Phase D Phase E S PD and ESAC review CD M T FA aunch E or extension GNSS+17, Ann Arbor (Michigan, USA), May /24

4 Objective and equirement Objective: To bring the cost of GEOS-ISS payload down by 50% equirement: Achieve ocean altimetry demonstration at 2 specular points simultaneously GNSS+17, Ann Arbor (Michigan, USA), May /24

5 Proposed GEOS-ISS Payload Simplification At science level: o Sequential polarizations (HCP and HCP) instead of parallel o Polarimetric adio-occultation removed At payload level: o Fewer, simpler and cheaper: F front-ends Beamformers Correlators o Knock-on effect on: power, on-board computer, thermal control, harness, mechanical design, data links, etc assembly, integration, test and schedule GNSS+17, Ann Arbor (Michigan, USA), May /24

6 Decrease in Front-ends by Antenna Element Sub-arraying 2 elements are removed (red crossed-out) the resulting array is divided in 14 sub-arrays each sub-array consists of a 2-element across-track array aser etro-eflector and Precise Orbit Determination antenna remain at the center position Along Track Across Track Number of Front ends BEFOE 30 emove 2 2 Group by 2 AFTE 14 GNSS+17, Ann Arbor (Michigan, USA), May /24

7 Antenna Element Sub-arraying: Impact in Performance 28 vs 30 elements 0.3 db antenna aperture degradation Element pattern at edge of swath (41 AT) 3 db loss To recover sensitivity 20 tilting of the arrays Scan angle reduced from 41 down to db gain Net degradation due to element sub-arraying: = 0.7 db GNSS+17, Ann Arbor (Michigan, USA), May /24

8 Antenna Array Tilt 2-element sub-array pattern with 20 physical tilt angle 2-element sub-array pattern in tilted array Across Track Nadir Angle GNSS+17, Ann Arbor (Michigan, USA), May /24

9 Beamformer eduction: Semi-swapping Direct signal T T eflected signal eflected signal Earth Earth UP UP x1 x2 x1 x2 DOWN Front-end DOWN Front-end b Back-end b Back-end a delay c a delay c GNSS+17, Ann Arbor (Michigan, USA), May /24

10 Semi-swapping: Only 1 Beamformer equired Direct signal T T eflected signal eflected signal Earth Earth UP UP x1 x1 DOWN Front-end DOWN Front-end b Back-end b Back-end a delay c a delay c GNSS+17, Ann Arbor (Michigan, USA), May /24

11 Semi-swapping: Impact in Performance Ocean observation time is halved sqrt(2) ranging degradation Altimetry requirement ( km) is expected to be still met by using interferometric GNSS- GNSS+17, Ann Arbor (Michigan, USA), May /24

12 Semi-swapping: Simplification in F Front-end F front-end original architecture GNSS+17, Ann Arbor (Michigan, USA), May /24

13 Semi-swapping: Simplification in F Front-end emoval of Beamformer B emoval of 2:1 switches improves noise figure by 0.4 db Acquisition of direct signal in HCP removed GNSS+17, Ann Arbor (Michigan, USA), May /24

14 Sequential Polarisations: Simplification in F Front-end HCP and HCP at F1 are measured sequentially instead of in parallel emoval of Beamformer C GNSS+17, Ann Arbor (Michigan, USA), May /24

15 eduction in Beamformers F1 F5 3 3 Up-looking Down-looking Down: = 12 Up = 12; Total = Up + Down = 24 GNSS+17, Ann Arbor (Michigan, USA), May /24

16 eduction in Beamformers: 2 reflection points instead of 4 F1 F5 Up-looking Down-looking Down: = 6 Up = 6; Total = Up + Down = 12 GNSS+17, Ann Arbor (Michigan, USA), May /24

17 eduction in Beamformers: Sequential Polarisations at F1 F1 F5 Up-looking Down-looking Down: = 4 Up = 4; Total = Up + Down = 8 GNSS+17, Ann Arbor (Michigan, USA), May /24

18 eduction in Beamformers: Semi-swapping F1 F5 Up-looking Down-looking Down: = 4 Up = 4; Total = Up = Down = 4 GNSS+17, Ann Arbor (Michigan, USA), May /24

19 eduction and Simplification in Beamformers: a Summary Before: 6 boxes each having 30 inputs x 4 beams Now: 1 simpler box having 14 inputs x 4 beams GNSS+17, Ann Arbor (Michigan, USA), May /24

20 eduction in Correlators: Before F1 F5 3 3 Up-looking Down-looking Correlators: = 12 GNSS+17, Ann Arbor (Michigan, USA), May /24

21 eduction in Correlators: After F1 F5 Up-looking Down-looking Correlators: = 4 GNSS+17, Ann Arbor (Michigan, USA), May /24

22 Correlator (PACO) Simplification Some of the upgrades proposed during the Phase A of the existing PACO FPGA are discarded: GNSS+17, Ann Arbor (Michigan, USA), May /24

23 GEOS-ISS Payload eduction Table GNSS+17, Ann Arbor (Michigan, USA), May /24

24 GEOS-ISS Science eduction Table GNSS+17, Ann Arbor (Michigan, USA), May /24