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Planet Labs Ground Station NetworkBryan Klofas
[email protected] April 2016
13th Annual CubeSat Developers WorkshopCal Poly SLO
• Planet Labs is driven by a mission to image the entire Earth every day, and make global change visible, accessible, and actionable
• 300+ employees• Based in San Francisco, CA
○ Satellite offices in Lethbridge and Berlin (RapidEye)• $183 Million in VC funding
• 133 satellites successfully launched• 2 rocket failures with 34 satellites lost (Orb-3, SpaceX-7)• 100 satellites successfully deployed• 32 satellites launched and waiting on ISS (Orb-4, OA-6)• 36 satellites still in orbit
Intro to Planet LabsSpace Startup
Slide 2
• 3U form factor with 6 fold-out panels• CCD camera• 20km swath width at 3.5m GSD from 400 km• Onboard JPEG2000 compression• 13 Hardware Revisions• COTS SSD• Ubuntu
A Typical SatelliteBasics
Slide 3
• UHF radio: TI wireless MCU• Power amplifier: RFMD 1 watt output• Monopole antenna
• Ground station is identical hardware and software• Presented at CubeSat Summer Workshop 2014
○ Design will be open-sourced soon (up and downlink encrypted and secured)
○ Follow-up presentation at SmallSat 2016
A Typical SatelliteUHF Radio
Slide 4
• S-band uplink○ 250 kbps BPSK○ NACK-based file protocol○ Needed for downlink ACM
• X-band downlink○ 12.5 Mbps up to 100+ Mbps○ 8.2 GHz at 2 watts○ DVB-S2 standard with Generic Stream Encapsulation○ Fixed 24 Mbaud symbol rate
■ Upgrade to 56 Msps on next sats○ Variable modulation: QPSK, 8PSK, 16APSK, 32APSK ○ Variable FEC: 1/4 up to 9/10○ GSE allows IP connectivity to satellite
A Typical SatelliteS/X Radio
Slide 5
• “Spaceship Captains” operate all satellites○ Mostly anomaly resolution and testing○ Normal operations: “Automate ourselves out of a job”○ If they all call in sick, everything still works (for a few days)○ 24/7 on call support for emergencies
• Mission Control is fully automated, runs on AWS○ Scheduling happens frequently○ All software done in house, allowing us to fix bugs quickly○ No existing products fit our needs
• System is fully automated and tolerant of missed passes○ Greatly reduced operational costs vs. 100% downlink
guarantee○ Missed data is downloaded next pass○ Decreased operational costs allow smaller team to manage
satellites and have a “normal” life (no graveyard shifts)○ Continuously developing/updating software
Satellite ControlOpen 9am-5pm M-F
Slide 6
• TT&C only• Uplink at 450 MHz, up to 100 Watts• Downlink at 401.3 MHz• Encrypted 4800 baud GFSK• Yaesu G-5500• Separate M2 yagis• Open-source radio design
A Typical Ground StationUHF
Morehead State University
Slide 7
• When not scheduled to talk with a satellite, each ground station opportunistically ranges with all available satellites
• Post processed errors at 1 day:○ JSpOC: 1 to 3km○ UHF ranging: 0.5km
• Ranging data fed back into Space Data Association
• Open orbit data at http://ephemerides.planet-labs.com
• See AAS 15-524, “Orbit Determination and Differential-Drag Control of Planet Labs CubeSat Constellation,” by Cyrus Foster, Henry Hallam, James Mason
A Typical Ground StationUHF Ranging
Slide 8
• 5m dish• Combined S/X feed• Up to 100 W S-band uplink• 29 dB/K at X-band• Integrated UHF feed on
other dishes• Dektec PCI DVB-S2
receiver card
A Typical Ground StationWashington State
Brewster, Washington
Slide 9
• 55 degree max elevation• X-band lock for 435 seconds = 7.25 min• Variable data rate up to 84 Mbps• Modcod up to 24• Downloaded: 4.2 GBytes = 650 pictures = 170k sq km *• Pictures uploaded to AWS for rectification
A Typical PassWashington State talking with Flock 2b, March 16th
* Including frame overlap, clouds, ocean, etc. Only 20-50% of downloaded pics are acceptable for consumers
Slide 10
An Average DayNew Zealand schedule for March 16th UTC
Spa
cecr
aft I
D
Slide 11
• 33 passes scheduled for 16 satellites• 25 passes successful, 75%
○ Satellite not transmitting or pointing correctly, ground station pointing error, software bugs
• 99 GBytes downloaded = 23k pictures = 6M sq km *
An Average DayNew Zealand on March 16th UTC
Slide 12
The Ground Station NetworkGlobal View
• 7 CGC 5m dishes• 7 Omnispace/ICO 7.6m dishes• 4 L3 Datron 5m dishes• 32 yagi stations
HSD + LST
Slide 13
A Typical DayGlobal View
Colors indicate ground station
Spa
cecr
aft I
D
Slide 14
A Typical DayMarch 16th UTC
● UHF:○ 333 passes scheduled, 239 good passes, 71%○ 97k commands received
● X-Band:○ 207 passes scheduled, 157 good passes, 76%○ 559 GBytes downloaded = 161k pics = 39M sq km *○ CONUS is 8M sq km
● Best day: 777 GB
Slide 15
• Image all the earth, every day• 6 TBytes of land images to download every day
○ Equipment already installed in Iceland○ More locations to come later this year○ Continuous improvement process○ Increasing downlink rate past 75% allows
us to download oceans, ice, etc
Mission 1Image all land, every day
Slide 16
Questions?