Building HW/SW to receive the GOES satellites Pieter Noordhuis -- KK6VXV

Transcription

1 Building HW/SW to receive the GOES satellites Pieter Noordhuis -- KK6VXV

2 Outline Antenna system and receiver Signals and demodulation/decode Challenges

3 But first

4 Types of satellites Polar Orbiting Environmental Satellites (POES) NOAA-18 (2005), NOAA-19 (2009), NOAA-20 (2017) METOP-A (2006), METOP-B (2013) Sun-synchronous orbit ( mi) Orbital plane rotates as earth orbits the sun (~1 per day)

5 Types of satellites Geostationary Orbiting Environmental Satellites (GOES) GOES-14 (2009, 105 W, on-orbit storage) GOES-15 (2010, 135 W, west ) GOES-16 (2016, 75 W, east, NEW) Geosynchronous equatorial orbit (22,236 mi)

6 The signals LRIT -- Low Rate Information Transmission HRIT -- High Rate Information Transmission Combined stream of EMWIN and LRIT data GOES-P (15) 2010 EMWIN / LRIT OQPSK / BPSK 17,970 / 293,833 GOES-R (16) 2016 HRIT BPSK 927,000 GOES-S 2018 (March) HRIT BPSK 927,000

7 The data products EMWIN (Emergency Managers Weather Information Network) LRIT (Low Rate Information Transmission) Image data Full Disk / Northern Hemi / Southern Hemi Visual, Infrared, Water Vapor Relays from Himawari-8, Meteosat, GOES siblings NWS DCS (Data Collection System)

8 Antenna system 1.9 GHz 22 dbi Parabolic Grid LRIT/HRIT is ~1.7 GHz but works fine Mount at 45 to match G16 polarization Type N connector Available at L-com for ~$85

9 Antenna system 12V Murata DC-DC 5V out 5V LNA 1: ZX60-242GLN-S+ Filter: VBFZ-1690-S+ 5V Bias T LNA 2: SPF5189

10 Antenna system LNA1: Mini Circuits ZX60-242GLN-S+ (~$50) 1710 to 2400 MHz, 28dB gain Filter: Mini-Circuits VBFZ-1690-S+ (~$40) Center frequency 1690 MHz (perfect for LRIT/HRIT) But wide passband (2dB): 1455 to 1925 MHz LNA2: SPF5189 (~$8 on ebay) 50 to 4000 MHz, 18dB gain General purpose LNA, useful to stock up

11 Antenna system Hammond enclosure mounted at dish 2x Amphenol RF bulkhead adapter 20ft of LMR-400 to receiver

12 Receiver hardware Raspberry Pi 3 running Raspbian Linux SDR with at least 8 bit ADC and 2M samples/sec Airspy Mini (12 bit, 3M or 6M samples/sec) RTL-SDR (8 bit, max 2.4M samples/sec) Bias T to power LNAs (optional) current sensor

13 Receiver hardware Custom board for power and mounting (OSH Park) Input 12v; DC-DC to 5v to power RPi Switch 12v; buffered MOSFET INA219 current sensor (Adafruit) no Powerpole yet

14 Receiver hardware: wrapped up

15 Before we move on...

16

17

18 :00:42 UTC GOES-16 ABI false color (channel 2 and 13) -- false color map by Harry Dove-Robinson

19 telemetry GOES-16 HRIT ~1.2 MHz ~8dB

20 Receiver: demodulator Turn the raw samples into bits The signal is always on; demod must be real time HRIT is ~identical to LRIT with higher data rate Both use BPSK modulation (Binary Phase Shift Keying) LRIT HRIT MHz MHz symbols/sec 1.3 GB/day symbols/sec 4.3 GB/day

21 Receiver: demodulator Automatic Gain Control Goal: normalize signal power Throughput RPi: 71 MSPS/core

22 Receiver: demodulator Costas tracking loop Goal: phase tracking Frequency offset rotation Throughput: RPi: 20 MSPS/core Fast NEON sin/cos implementation Note: Local oscillator jitter/drift Satellite doppler (even in geostat.)

23 Receiver: demodulator Root raised cosine filter Goal: filter signal Complements filtering of transmitter Throughput RPi: 10 MSPS/core (with N=31 taps)

24 Receiver: demodulator Clock recovery Goal: turn samples into symbols Asynchronous system; no clock signal Throughput RPi: 17 MSPS/core With ~3 samples per symbol

25 Receiver: demodulator Before After

26 Receiver: decoder We have a bitstream now what? Forward error correction: Rate ½ convolutional code (2 bits per bit) Given bitstream, find most likely path Doesn t help for longer (> a few bits) noise bursts

27 Receiver: decoder 8192 bit frames 64 bit sync word: 0x1ACFFC1D 892 bytes of data 128 bytes of Reed-Solomon code Code applies to 4 interleaved blocks of 223 bytes Short noise burst means all code can be used Derandomization Demodulator relies on frequent level transitions Randomization means a packet of zeroes is OK

28 Receiver: decoder Virtual Channel Data Units (fixed length frames) Associated with Virtual Channel Contains part of one or two Transport Protocol Data Units Transport Protocol Data Units (max size 64 KB) Associated with Application Process Identifier (APID) One or more form a Session Protocol Data Unit Session Protocol Data Units (no max size) Equivalent of a file; variable length All session PDUs have an LRIT header

29 Example LRIT header Primary (0): File type: 0 (Image Data) Header header length (bits/bytes): 32696/4087 Data length (bits/bytes): / Total length (bits/bytes): / Image structure (1): Bits per pixel: 8 Columns: 2000 Lines: 2000 Compression: 1 Image navigation (2): Projection name: geos(-75.0) Column scaling: Line scaling: Column offset: 2960 Line offset: 8320 Image data function (3): Data: (omitted, length: 3064)

30 Example LRIT header (cont d) Annotation (4): Text: OR_ABI-L2-CMIPM2-M3C02_G16_s _e _c lrit Time stamp (5): Time stamp: :29:32 Ancillary text (6): Text: Time of frame start = T17:28:56.9Z Satellite = G16 Instrument = FM1 Channel = 2 Imaging Mode = ABI Mode 3 Region = Mesoscale Resolution = 0.5km at nadir Segmented = no NOAA LRIT (129): Agency signature: NOAA Product ID: 16 Product SubID: 0 Parameter: 0 NOAA-specific compression: 1

31 :28:56 UTC GOES-16 ABI channel 2 - mesoscale region 2 Snowy Midwest

32 :28:56 UTC GOES-16 ABI channel 2 - mesoscale region 2 Snowy Midwest

33 :28:56 UTC GOES-16 ABI channel 2 - mesoscale region 2 Snowy Midwest

34 And it can all run on a Raspberry Pi!

35 Power Task Current 12V) Power (W) Raspberry Pi 3 (idle) Switch on LNAs Start sampling Start demod/decode Total

36 QRM: The good

37 QRM: The bad

38 QRM Looks bursty and splattery; perhaps pagers? Better dish / better filtering Don t let it confuse the demodulator

39 Resources

40 Thanks Writing open source GOES decoder in Open Satellite For showing the mesh dish has enough gain for Creating awesome false color LUT for GOES-16

41

42