1 / 18

Ground support network for the Metop GRAS atmospheric sounding mission

Ground support network for the Metop GRAS atmospheric sounding mission. R.Zandbergen, A.Ballereau, M.Lorenzo, J.M.Dow, C.Marquardt, F.Wollenweber 18 April 2008. G NSS R eceiver for A tmospheric S ounding G round S upport N etwork. … on board Metop. GPS signal travels through atmosphere

pahana
Download Presentation

Ground support network for the Metop GRAS atmospheric sounding mission

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Ground support network for the Metop GRAS atmospheric sounding mission R.Zandbergen, A.Ballereau, M.Lorenzo, J.M.Dow, C.Marquardt, F.Wollenweber 18 April 2008

  2. GNSS Receiver for Atmospheric Sounding Ground Support Network … on board Metop

  3. GPS signal travels through atmosphere Through relative S/C motions, occultation profiles are generated Fore and aft antennas on Metop allow monitoring of both setting and rising occultations Two occultations can be observed by each antenna Max. per day per satellite ~500 occ. Atmospheric Sounding

  4. EUMETSAT will operate three Metop S/C (polar LEO) … and generate atmospheric sounding products in NRT … for delivery to European Met Offices within 3 hours The generation of profiles requires precise orbits and clock solutions for both Metop and the occulting GPS satellite Metop POD to be performed in-house, using GRAS GPS receiver (zenith antenna) The GPS products are considered ‘Support Data’, to be provided externally Generation of sounding profiles

  5. GPS orbits (for Metop POD and occultation processing) GPS clock solutions Low-rate for Metop POD High-rate for occultation processing EOP data (for Metop POD) Auxiliary data (TZD, Meteo, Nav msg…) Support data for occultation processing

  6. GPS orbits (for Metop POD and occultation processing) GPS clock solutions Low-rate for Metop POD High-rate for occultation processing EOP data (for Metop POD) Auxiliary data (TZD, Meteo, Nav msg…) High-rate, selected, ground receiver data High-rate ground clock solutions Support data for occultation processing } why?

  7. Supporting differenced processing methods

  8. Method 1: undifferenced Method 2: eliminate GRAS clock Method 3: take out the GPS clock (replace by ground clock) Method 4 not yet implemented For method 3, accurate ground clock solutions and ground tracking data of the occulting satellite are required EUMETSAT deliver a table of predicted occultations to ESOC and ESOC return the necessary ground data (SSD) Ground (Sounding) Support Data

  9. The most fundamental requirements were studied in 2001: Timeliness: 60 min. for orbits and clocks Clock accuracy: 1 ns at 2-sigma for each satellite Clocks to be interpolated at 50 Hz GPS satellite velocity accuracy requirement! Guaranteed high availability (99% & limited interruptions) Can be operated for 15 years, 2 satellites in parallel Extensible to other missions with similar requirements Support data key requirements

  10. A dedicated and fully redundant network of approximately 20 sites (i.e. in total 40) Resulted in contracts with existing network operators: GFZ, NRCan and Fugro Seastar A processing centre in ESOC GPS orbits computed every 3 hours, delivering predictions Clocks computed every 15 minutes, not predicted To support the 50 Hz GRAS data rate, compute and deliver 1 Hz GPS clocks (not interpolated) High-level design

  11. The GSN Network (prime sites)

  12. Using predicted orbits, batch 1-Hz clock determination every 15 minutes for 23 minute arcs (15 + 8 minutes overlap) Key issue: timing of the clock products

  13. Successful validation of GRAS GSN in February 2006 Launch of the first satellite (Metop-2) October 2006 Activation of GRAS GSN operations one month prior to launch First year of operations completed September 2007 Accuracy and availability requirements met by a good margin (first year availability 99.71%) Support to COSMIC mission has started Current status

  14. Requirements verification by comparing to IGS finals Accuracy requirements are met almost continually Accuracy requirements from EUMETSAT equivalent to 95-percentile In IGS terms (‘typical RMS’), orbit prediction accuracy based on the relatively small network is around 10 cm. Clock accuracy is corresponding to this (around 0.3 ns, removing only a single common clock bias) Achieving the accuracy requirements

  15. NRT orbit and clock accuracy (Nov. 2007)

  16. Operational level-2 data will be provided by GRAS SAF Validation of these results in progress Preliminary GRAS results

  17. Acknowledgments are due to: • Station network providers: • Météo France Tahiti For the excellent quality of their support and data products • The EUMETSAT team: F. Wollenweber, C.Marquardt, Y. Andres • The ESOC team: ESA: A. Ballereau, R.Zandbergen, J.M.Dow GMV SA: M. Lorenzo, P. Alfaro, J. Tegedor, I. Romero, F. Lopes Pereira, C. Garcia, J.Fernandez

More Related