Update of GPS systems technical specifications and challenges

Transcription

1 Update of GPS systems technical specifications and challenges GPS Communication Power Bjorn Johns September 7, 2005 Polar Technology Workshop Washington, DC

2 GPS receivers State-of-the-art in 2005: Power: ~2W 1 Gb on-board memory <$10,000 with DM chokering antenna Observables: Track all-in-view GNSS satellites, L1, L2, C/A, P (Y), L2C, GLONASS Communication protocol: serial and IP Easy field downloads: removable CF memory or just swap receivers Reliability: real-world MTBF > 4 years Extreme cold environment not a big issue Mature, commercially available, solid-state, consumer electronics

3 Some off the shelf GPS choices Novatel Trimble SCIGN radome DM IGS standard chokering antennas Topcon Dana Caccamise/Eddie Wheeler Tech 2000

4 TAMDEF receiver use

5 GPS receiver challenges All features are not provided in one product typically issue a wish-list RFP and make tradeoff decisions New products are plagued by hardware and firmware flaws require rigorous testing, follow-up, and vendor response Custom firmware for unique needs of academic community and extreme environment Don t know real MTBF in advance operational field experience is essential before committing to a particular model in the Antarctic

6 Communications for GPS summary Why: Data users benefit from low latency data retrieval Why: Advance knowledge for station maintenance and troubleshooting Why: Streamlining of downstream data quality control and processing GPS data volume < 1Mb/day Adds 1W to power budget Cost: Radio modem $1,500 and no recurring Iridium modem $1,500 plus recurring airtime cost A three-tiered approach for GPS data retrieval: 1. Line-of-sight radio links and repeaters proven for IP and serial comms an Internet node 2. Commercial satellite-based connection (e.g., Iridium) if the distance to an Internet node exceeds the distance capability of radio modems 3. Onboard memory will serve as backup in the event of loss of the communication link, allowing for manual data retrieval during the next maintenance visit or opportunity visits.

7 Radio communications proven FreeWave radios used by community since mid 1990s Transantarctic sites Mt. Erebus sites UNAVCO global applications, EarthScope Erebus site HOOZ

8 Mt. Erebus repeater can serve TAM sites

9 Iridium communication test at TAMDEF site Fishtail Point

10 Communications for GPS challenges Iridium data link reliability latency, disconnects, and lock-ups Custom hardware solutions Future satellite solutions? Integrating GPS and seismic state-of-health into one data link Keeping on-site smarts to a minimum Managing summer vs. winter comms for powersaving System integration: GPS/modems/download software/delivery to data archive

11 Autonomous test-bed site built this summer, McMurdo deployment planned for October 2005

12 Radio link GPS data communications flow Mt. Erebus Repeater Burn-in and test integrated system, communications link UNAVCO network monitoring and data archive Deploy system to field after burn-in Remote site Self-contained McMurdo test-bed RADARSAT/ Bldg 71 Internet access Remote GPS data collection On-line data access

13 Iridium link GPS data communications flow Iridium LEO satellite communications system Burn-in and test integrated system, communications link UNAVCO network monitoring and data archive Deploy system to field after burn-in Very remote site Self-contained McMurdo GPS test-bed Very Remote GPS data collection On-line data access

14 Mt. Erebus dataflow from Hooper s Shoulder

15 CONZ state-of of-health info

16 Power systems for GPS GPS receiver system total power budget <5W (GPS, comms, ancillary) Photovoltaics and sealed lead acid battery power systems well understood, but heavy and temperature limited Solar-only brute force : 160W PV array, 2700Ah battery bank for year-round operation, 5W system at 80 deg S ($3500, 2000lb) Wind turbines: Promising, used successfully with GPS systems on Erebus and at Mt. Coates

17 TAMDEF site FLM2 Solar

18 Ampair turbine at Erebus site HOOZ Wind

19 Power systems for GPS - challenges Better (and affordable) battery technology: cold performance, energy density One-time lithium or air cell batteries for reserve Wind turbine reliability, set-up Power saving measures: near year round operation, comms only in summer Insulated enclosures bulk vs. cost vs. longevity

20 Insulated enclosures R-25 big box

21 Complete system

22 GPS component matrix Item Power Cost Weight Data rate Receiver w/choke 2.5W $10,000 10lb 750kb/day Battery 100Ah $120 70lb Solar panel frame $200 40lb Solar panel 80W $350 25lb Enclosure $700 40lb Iridium modem 1W $1,500 2lb 2,400bps Radio modem 1W $1,500 2lb 56kbps GPS antenna mount $500 15lb Power board 30A $350 2 lb

23 Key GPS technical points: No major extreme environment problems for GPS sensors GPS systems can be readily deployed for spring-summer-fall only operation Advanced battery technology and reliable wind systems desired for year-round operation Thorough system integration, testing, operation and maintenance is necessary for success Challenges well within reach of an organized community effort