DICE Telemetry Overview and Current Status

Transcription

1 DICE Telemetry Overview and Current Status CubeSat Workshop, April 2012 Jacob Gunther

2 Overview DICE telemetry overview Operations experience and timeline Narrowband interference mitigation Frequency domain interference suppression Multi-antenna interference cancellation

3 DICE CubeSats (X2) Cadet-U

4 DICE Telemetry Systems (3 Mbit/s) db Gain With FEC the throughput is 2.69 Mbps on downlink

5 Operations Experience Circles: 10 degree horizon projected to 500 km altitude. Catalog Name Launch Date Period Incl. Apogee Perigee DICE DICE March 10, 2012 October 28, 2011

6 Timeline Nov. Dec. Jan. Feb. Mar. Apr. May Wallops 1 st contact Wallops g.s. offline Wallops g.s. online SRI 1 st contact 465 MHz operations Original demodulator software 468 MHz operations RFI cancellation New radio software 10-20% of data recovered 50% of data recovered 100%???

7 Spectrogram Our signal NBFM interference Y287500c_500_1000 Wallops Island, Virginia

8 Wallops and SRI Signals

9 RF Environment in Vicinity of Ground Station

10 Narrowband FM Interferers

11 Interference at the SRI Site Housing/athletics, Facilities/events, Facilities talkaround, Grad. Business school, IT support,

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13 Wallops Island Ground Station

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15 Telemetry System WBX MHz Rx/Tx Ethernet

16 OQPSK Demodulator WBX FPGA GnuRadio C Demod. USRP PC Workstation AGC Phase Recovery Matched Filter Interp. Decision FEC Decoder C Demod. Phase PLL Timing PLL

17 Pre-detection Variables AGC Phase Recovery Matched Filter Interp. Decision C Demod. Phase PLL Timing PLL

18 Spectral Modification (preserve phase) Set this to this Power spectral density Actual signal spectrum (dotted) Fitted model (red)

19 Before and After

20 IFFT & Overlap-Add

21 Spectrograms: Before and After

22 Pre-detection Variables AGC Phase Recovery Matched Filter Interp. Decision C Demod. Phase PLL Timing PLL

23 With Interference Interference Canceled

24 Yahtzee c Farkle F1500a 20 db power disparity

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27 Yahtzee c 20 db power disparity Farkle F1500a

28 Interference at SRI Site Interference at Wallops Site

29 Looking to the future of MHz auxiliary antenna or antenna array 1 Watt 2-20 Watt main antenna (high-gain, 36 db) Place auxiliary antenna near main antenna High-gain antenna collects satellite signal + interference Auxiliary antenna sees only interference Provides two independent looks at interference Use digital signal processing to cancel interference Leaves the desired signal untouched

30 Adaptive Interference Cancellation main antenna aux. antenna physical model of measurements digital signal processing minimize E[e(t)] 2 = linear prediction of x 0 (t) using x 1 (t)

31 Housekeeping Data Internal Temperatures External Temperatures Transmitter on 1 day

32 Magnetometer Data

33 Summary Interference at 465 MHz 1. Software modifications More robust demodulator Added interference cancellation 2. Moved carrier frequency from 465 to 468 MHz Pointing problems: Wallops, Jan. 1 Feb. 15 Periodic lock-ups of the satellites Second ground station at SRI, Mar. 10, 2012 Steadily improving and getting more science data down and into database MHz band can be used for high-speed downlink Willing to share what we have learned about frequency licensing with the NTIA

34 Backup Slides

35 Regulations The Law The NTIA US Frequency Allocations The ITU All satellites go through international licensing Category of usage Earth to Space Space to Earth Amateur MHz 2.4 GHz ISM industrial, scientific and medical MHz GHz Government (Primary) MHz MHz 450 MHz GHz GHz

36 NTIA Red Book Table on MHz Must read the notes Lower case means secondary user

37 Regulations on 460 to 470 MHz Earth exploration-satellite service applications, other than the meteorological-satellite service, may also be used in the bands MHz and MHz for space-to-earth transmissions subject to not causing harmful interference to stations operating in accordance with the Table. US201 In the band MHz, space stations in the Earth exploration-satellite service may be authorized for space-to-earth transmissions on a secondary basis with respect to the fixed and mobile services. When operating in the meteorological-satellite service, such stations shall be protected from harmful interference from other applications of the Earth exploration-satellite service. The power flux-density produced at the Earth s surface by any space station in this band shall not exceed -152 dbw/m²/4 khz. 10 MHz Bandwidth available

38 Definitions Earth Exploration-Satellite Service: A radiocommunication service between earth stations and one or more space stations, which may include links between space stations, in which: information relating to the characteristics of the Earth and its natural phenomena including data relating to the state of the environment is obtained from active sensors or passive sensors on earth satellites; similar information is collected from active sensors or passive sensors on Earth satellites: airborne or earth-based platforms; such information may be distributed to earth stations within the system concerned; platform interrogation may be included. This service may also include feeder links necessary for its operation. Meteorological-Satellite Service: An Earth exploration-satellite service for meteorological purposes.

39 Getting a License from the NTIA 1. Certification Demonstrate that the system concept and equipment components will work appropriately NTIA engineer will review and approve EL-CID electronic certification 2. Frequency assignment 465, 468 MHz 3. Must do for up/down links 4. We will share Cadet-U (downlink) CC1101 (uplink)

40 Frequency License MHz Band Frequency Allocation Started (7/20/2011) Completed (8/25/2011) The DICE team would like to express gratitude to Andy and the NTIA for processing the DICE application in record time. 7/20/ The DICE certification request has been submitted. There is no chance whatsoever that we will obtain certification and authorization by August 25, 2011, so that should be stricken from the list of scenarios right off the bat. -Andy Clegg (NSF Spectrum Manager) 8/25/2011 Attached are the approved frequency assignments for the DICE ground stations, suitable for framing. The spacecraft assignment was sent previously (NSF ). This completes all of the needed paperwork. -Andy Clegg (NSF Spectrum Manager)