GNSS Reflectometry at GFZ

Transcription

1 GNSS Reflectometry at GFZ Achim Helm, Georg Beyerle, Ralf Stosius, Markus Rothacher (GFZ) External Partners and Contributors: Oliver Montenbruck (DLR), Estel Cardellach, Antonio Rius (IEEC), Sergei Yudanov, Javad Ashjaee (JAVAD GNSS) Marc-Peter Hess (EADS Astrium) Markus Nitschke (now TRIMBLE) Thomas Gruber (now TU Munich) Slide 1

2 passive bistatic reflectometry and interferometry: PARIS concept M. Martın-Neira, A Passive Reflectometry and Interferometry System (PARIS): Application to Ocean Altimetry, ESA J., vol. 17, pp , Figure from: Altimetry precision of 1 cm over a pond using the widelane carrier phase of GPS reflected signals M. Martin-Neira, P. Colmenarejo, G. Ruffini, and C. Serra, Can. J. Remote Sensing, Vol. 28, No. 3, pp , 2002 The difference in time-of-arrival (TOA) between direct and reflected signals provides altimetry information The shape of the reflected signal provides sea surface characteristics information Slide 2

3 GNSS-R (Reflectometry) observation types in/coherently reflected signals: code phase altimetry coherently reflected signals: carrier phase altimetry elevation angle delay incoherently reflected signals: scatterometry coherent Slide 3

4 Predicted specular reflection points as seen by a GNSS receiver onboard ISS increase of spatial coverage by using all available GNSS signals ISS GPS+GLONASS+GALILEO Slide 4

5 Space-borne GNSS-R: Multisatellite Constellation Simulation increase of temporal coverage by raising number of receiver satellites and orbits data coverage within 15 minutes: Constellation of 18 LEO satellites distributed on 3 different orbit planes Slide 5

6 CHAMP altimetry reflection angles T. Gruber, pers. com., 1997 Slide 6

7 Flying nadir-looking LHCP GPS antenna on CHAMP in space Slide 7

8 coherent GPS reflections observed by CHAMP signatures of coherent reflection in CHAMP GPS 50 Hz occultation data GPS CHAM P direct ray satellit e reflection geometry in space reflected ray Earth tangent point reflection point CHAMP G. Beyerle and K. Hocke, Observation and simulation of direct and reflected GPS signals in radio occultation experiments, Geophys. Res. Lett. 28 (9), , 2001 E. Cardellach et al., Carrier phase delay altimetry with GPS-reflection/occultation interferometry from low Earth orbiters, GRL, 31, L10402, doi: /2004gl019775, 2004 Slide 8

9 GFZ flight campaign lake Constance (March 2004) air-borne GPS altimetry based on L1 CA code flight height above ground from GPS reflection of PRN 3 true flight height above ground L1 Zarlink based Comnav receiver time [min] time [min] Slide 9

10 open-loop tracking with the GFZ OpenGPS L1 receiver slave correlation slave correlation slave correlation slave correlation slave correlation channel channel channel channel channel correlation power code offset tracking master correlator channel: early arm prompt arm time [chips] in-phase quad-phase phase amplitude relative height Slide 10

11 GPS altimetry based on L1 carrier phase observations Mount Fahren 1625 m asl Lake Walchen 801 m asl Lake Kochel 599 m asl 2cm height accuracy A. Helm et al., Detection of coherent reflections with GPS bipath interferometry, under review Slide 11

12 GPS altimetry at the baltic sea based on L1 carrier phase observations Slide 12

13 Problem: influence of local troposphere Slide 13

14 Natural hazard Monitoring with GPS altimetry Slide 14

15 the 2005 Merzbacher glacier lake outburst: GPS reflections from ice-covered water surface July 30, 2005 H=3227.3m (-46.0m) August 3, m H=3213.8m (-59.6m) A. Helm, H.-U. Wetzel, W. Michajljow, G. Beyerle, Ch. Reigber and M. Rothacher. NATURAL HAZARD MONITORING WITH REFLECTED GPS SIGNALS AT MERZBACHER GLACIER LAKE pages: Publikationen der Deutschen Gesellschaft für Photogrammetrie, Fernerkundung und Geoinformation e.v. DGFP Tagungsband 16 / 2007, ISSN Eckhardt Seyfert, Hrsg. Slide 15

16 GORS receiver prototype Helm, A.; Stosius, R.; Beyerle, G.; Montenbruck, O.; Rothacher, M. (2007): Status of GNSS reflectometry related receiver developments and feasibility studies within the German Indonesian Tsunami Early Warning System, IEEE International Geoscience and Remote Sensing Symposium - IGARSS 2007 (Barcelona, Spain 2007), commercial of-the-shelf JAVAD GeNeSiS-112 OEM receiver boards Size: 112 x 100 x 14 mm Weight: 110 g Avg. Power: 2.7 W 72 GNSS signal channels one RF frontend GNSS signals: GPS L1/L2, GPS L2C, (GLONASS) modifications: 200 Hz output of in-phase, quad-phase data (I,Q) for GPS L1 C/A, L2, L2C open-loop/channel slaving (1 channel) for GPS L1 C/A, L2C Slide 16

17 GPS L1/L2 space signal simulator tests histogram of tracked satellites in the orbital frame number of tracked satellites over a 12 h arc GORS receiver prototype connected via ext. LNA to the Spirent GSS7700 at DLR L1 C/A code tracking noise 17cm carrier phase noise 0.7mm GORS prototype can acquire and track GPS signals under low Earth orbiter signal conditions 515 km orbit height, polar, sun synchronous GORS A GNSS Occultation, Reflectometry and Scatterometry Space Receiver A. Helm, O. Montenbruck, J. Ashjaee, S. Yudanov, G. Beyerle, R. Stosius, and M. Rothacher Proceedings of the 20th International Technical Meeting of the Satellite Division of The Institute of Navigation ION GNSS 2007, Sept , 2007, p Slide 17

18 GPS L1 C/A + GPS L2C Carrier Phase Altimetry Measurements Mount Fahren PRN 17 at 13 elevation Lake Walchen Δh 825m Tide Gauge Helm, A.; Stosius, R.; Montenbruck, O.; Yudanov, S.; Beyerle, G.; Rothacher, M.: Ground-based water level observations at Lake Walchen with reflected GPS L1 C/A and L2C signals. In: Geophysical Research Abstracts, EGU General Assembly 2008 Vienna, SRef-ID: /gra/EGU2008-A-01170, Apr. 17, GPS L1 C/A GPS L2C Slide 18

19 Ground-based GNSS-R: Scatterometry Measurement & Modelling GPS L1 C/A GPS L2C Helm, A.; Stosius, R.; Montenbruck, O.; Yudanov, S.; Beyerle, G.; Rothacher, M.: Ground-based water level observations at Lake Walchen with reflected GPS L1 C/A and L2C signals. In: Geophysical Research Abstracts, EGU General Assembly 2008 Vienna, SRef-ID: /gra/EGU2008-A-01170, Apr. 17, Slide 19

20 Outlook 2008 GORS and GORS 2 GORS: GPS L1 + L2C, 72 channels May 2008: increased number of slave channels to 10 GORS2: GPS L1 + L2C + GLONASS + GALILEO, 216 channels, multiple (1-4) RF frontends, external frequency input implement GORS functionality Extend signal processing to GLONASS + GALILEO repeat signal simulation perform space hardware tests Slide 20

21 Air-borne GNSS-R: Zeppelin NT and HALO Slide 21

22 possible GORS flight opportunity on space shuttle in March 2009 ppcbox In Orbit Technology Demonstrator Possible in-orbit validation of GORS2 receiver and a SensorSystems Antenna during shuttle flight to the ISS M-P. Hess, EADS Astrium, personell communication, 2008 further running space activities related to GORS/GORS2: Flying Sensors (TU-Berlin/GFZ), DLR Kompaktsatelliten Mission (DLR/GFZ), Formosat Follow-on (NSPO) ACES experiment on ISS Slide 22

23 ACES GORS2 receiver as secondary payload on ACES mission for GNSS remote sensing on ISS Slide 23

24 summary and outlook First successful steps toward a multi-frequency GNSS-R COTS receiver achieved using GPS L1 and L2C GORS prototype successfully acquired and tracked GPS signals under simulated low Earth orbiter conditions, but further investigations have to be done Coherent carrier phase observations of L1 C/A and L2C signals, using 200Hz I,Q data Incoherent reflection observation with up to 10 independently steerable correlator channels Switch to GORS2 Javad Triumph HW Extend reflected signal reception to GLONASS and civil GALILEO signals Extend number of RF frontends in order to work with RHCP and LHCP antennas in parallel Thermal vacuum and total ionization tests of the GORS2 prototype Transition from ground-based to air-borne and space-borne measurements Critical: HW availablility and development time/acess to receiver SW Slide 24