GNSS Remo Sensing in ensin a 6U Cubesat

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1 GNSS Remote Sensing in a 6U Cubesat Andrew Dempster

2 Remote Sensing using GNSS Radio occultation Well established, with existing missions, v useful for input to weather models Reflectometry Experimental, some flights Other Interference monitoring? GNSS Remote Sensing: 6U Cubesat Workshop 2

3 Radio Occultation (RO) GPS/ MET 1995 was the first experiment Other missions: 9 launched, 8 planned GNSS Remote Sensing: 6U Cubesat Workshop 3

4 Radio Occultation (RO) Limb-sounding GNSS Remote Sensing: 6U Cubesat Workshop 4

5 Radio Occultation (RO) COSMIC US/ Taiwan (Formosat) 6 microsatellite constellation COSMIC 2 6 low inclination ( ) 6 high inclination ( ) GPS/ Galileo/ Glonass GNSS Remote Sensing: 6U Cubesat Workshop 5

6 Radio Occultation (RO) GNSS Remote Sensing: 6U Cubesat Workshop 6

7 Radio Occultation (RO) To estimate iono/ tropo profiles from GNSS alone, need more observations More GNSS satellites/ systems Existing sensors coming to end of life More low-cost satellites needed GNSS Remote Sensing: 6U Cubesat Workshop 7

8 Reflectometry GNSS signals reflected from the surface Sea state/ wind speed Soil moisture Biomass Cryosphere mapping GNSS Remote Sensing: 6U Cubesat Workshop 8

9 Passive remote sensing using GNSS signals as a signals of opportunity Imaging only at the specular reflection points Upward RHCP Antenna Airborne/ Spaceborne Platform Surface Specular Reflection Point GNSS Reflectometry Direct RHCP Signal From GNSS SV Downward LHCP Antenna Indirect LHCP Signal From GNSS SV GNSS Remote Sensing: 6U Cubesat Workshop 9

10 GNSS-R from LEO From Innovation: Reflecting on GPS, by Scott Gleason, GPS World, 1 October GNSS Remote Sensing: 6U Cubesat Workshop 10

11 Normalised Correlation Power (db) Wind Speed Estimates (m/s) GNSS Based Sea State Estimation Surface wind speed estimation using delay waveform fitting m/s 3 m/s 3.5 m/s 4 m/s 4.5 m/s measured Time (C/A code chip) individual estimates 0.5 wind speed at Norah Head wind speed at North Head Satellites GNSS Remote Sensing: 6U Cubesat Workshop 11

12 Interference Found by accident by SSTL (GNSS) SMOS (passive microwave) Could design an interference detector GNSS Remote Sensing: 6U Cubesat Workshop 12

13 GPS Interference in GNSS-R M. Unwin, P. Blunt, R. de Vos van Steenwijk, S. Duncan, G. Martin, P. Jales, GNSS Remote Sensing and Technology Demonstration on TechDemoSat-1, Proc ION-GNSS, Portland, Sep 21-23, 2011 GNSS Remote Sensing: 6U Cubesat Workshop 13

14 Global L-band interference From SMOS satellite MHz GNSS Remote Sensing: 6U Cubesat Workshop

15 GNSS Remote Sensing: 6U Cubesat Workshop

16 GNSS Payload Redundancy? Frequencies? Systems? Positioning Receiver RHCP Reflectometry Receiver Radio Occultation Receiver LHCP Reflectometry Receiver.... GNSS Remote Sensing: 6U Cubesat Workshop 16

17 Namuru V3-2 is a GPS designed for LEO Suitable for use on a Boeing Colony II 3U cubesat Single frequency/ system Namuru V3-3 Namuru V3.2 and V3.3 Garada ASRP receiver GPS/ Galileo L1/ E1/ L5/ E5 GNSS Remote Sensing: 6U Cubesat Workshop 17

18 Why 6U? COSMIC wasn t big 40kg 8kg propellant (DV 450ms -1 ) 55W deployed solar panels (800km, 72 inclined orbits) GNSS Remote Sensing: 6U Cubesat Workshop 18

19 Steerable GNSS-R Array (1U) 1U Cubesat configuration Replace side panels with PCB with etched RF elements Assume 3 panels: 2 folding out Also applicable to a 3U cubesat Patch separation (75 80mm) < Half a wavelength (95 mm) GNSS Remote Sensing: 6U Cubesat Workshop 19

20 References Shuanggen Jin, G.P. Feng, S. Gleason, Remote sensing using GNSS signals: Current status and future directions, Advances in Space Research 47 (2011) pp GNSS Remote Sensing: 6U Cubesat Workshop 20