leveraging commercial broadband leo...
TRANSCRIPT
![Page 1: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/1.jpg)
Leveraging Commercial Broadband LEO Constellations for Navigation
Tyler Reid, Andrew Neish, Todd Walter, & Per EngeStanford University GPS Lab
September 16, 2016
ION GNSS+ 2016Portland, OR
![Page 2: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/2.jpg)
OutlineImportance of
GNSS
![Page 3: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/3.jpg)
3
More Applications Coming
![Page 4: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/4.jpg)
Drawbacks of GPS
• Dependent: We have become reliant on this now critical infrastructure for nearly all aspects of our lives.
• Easy to Jam: Can take out a city block with a 20 Watt GPS jammer.
• Goal: To increase GNSS resilience.
4
![Page 5: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/5.jpg)
Changing Space
• There has been a resurgent interest in building large constellations of low Earth orbiting (LEO) satellites to deliver broadband internet to the world.
• Proposals have been announced by OneWeb with support from Virgin and Qualcomm, SpaceX with support from Google, Boeing, and Samsung.
• Can these be leveraged as a platform for navigation by piggybacking with a hosted navigation payload?
5
![Page 6: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/6.jpg)
Hosted Payload
• WAAS is an FAA payload which has been hosted on a variety of commercial GEO satellites including Intelsat, Telesat, and Inmarsat.
• This shows WAAS on Intelsat’s Galaxy 15, a GEO telecommunications satellite.
6Source: Hosted Payload Alliance
![Page 7: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/7.jpg)
7
GPS (32) + Iridium (66)
![Page 8: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/8.jpg)
Satellite Footprint
8
MEO LEO
![Page 9: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/9.jpg)
Iridium (66)
9
![Page 10: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/10.jpg)
OneWeb (648)
10First launches 2017, initial operational capability 2019
![Page 11: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/11.jpg)
SpaceX / Samsung (4000+)
11First launches 2016, initial operational capability 2020
![Page 12: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/12.jpg)
12
All Operational Satellites
1,305 Operational Satellites Today
![Page 13: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/13.jpg)
Position Error
13
![Page 14: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/14.jpg)
σHOR = HDOP σURE
σURE
σVERT = VDOP σURE
14
![Page 15: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/15.jpg)
Error Budget
• What is our 3D position error?
15
σURE ✕ PDOP
User Range Error
Position Dilution of Precision
![Page 16: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/16.jpg)
16
16
GPSBeiDou
GalileoGLONASS
GDOP as a Function of Constellation Size
![Page 17: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/17.jpg)
Error Budget
• What is our 3D position error?
17
σURE ✕ PDOP
User Range Error
Position Dilution of Precision
![Page 18: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/18.jpg)
What Does URE Need to Be?
18
Horizontal Vertical SIS URE
GPSGlobal DOPS / URE Analysis (95%)
3.309 m 4.860 m 0.8 m
OneWebGlobal DOPS / URE Analysis (95%)
2.864 m 4.773 m 3.0 m
*A constellation like OneWeb could have a URE 3x worse and give comparable positioning performance.
1William J. Hughes Technical Center Federal Aviation Administration GPS Product Team, Global Positioning System (GPS) Standard Positioning Service (SPS) Performance Analysis Report, Report #86, 2014.
![Page 19: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/19.jpg)
How do We Get That URE
• Clocks– Need to use clocks that get comparable performance to
GPS.
• Orbit– Orbit ephemeris.
– Constellation-wide orbit determination.
• Cost– How can this be done at a lower than traditional cost? We
want this to make sense for a hosted payload in LEO.
19
![Page 20: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/20.jpg)
Clocks
• Each GPS satellite has 4 atomic clocks onboard.
• Each costs millions of dollars and consume ~40 Watts.
• They are too costly in terms of $’s and power for low cost LEO.
20
![Page 21: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/21.jpg)
Chip Scale Atomic Clock (CSAC)
21
Source: Symmetricom
• Low Power: <120mW
• Small Size: 17 cc volume, 1.6”x1.4”x0.5”
• Low Cost: ~1000$, projected to be ~$300 in coming years.
• Trade off: ~100x worse at one day compared to GPS clocks.
• Can get comparable performance if you update once per orbit (100 minutes) instead of once per day.
![Page 22: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/22.jpg)
Orbits
• With the CSAC, we need to know the orbit within a 3D RMS position of 5 meters (~3 meters in along track, cross track, and radial directions – all equally important in LEO).
• Ephemeris accuracy will be largely based on the orbit determination, prediction, and parametrization.
22
![Page 23: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/23.jpg)
+Higher Order Gravity
+Atmospheric Drag
+Third Body Gravity
+Solar Radiation Pressure
Satellite Motion = Spherical Gravity Field + …
![Page 24: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/24.jpg)
24
24
Perturbation Forces as a Function of Altitude
![Page 25: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/25.jpg)
GPS Ephemeris
25
6 KeplerianOrbital ElementsCorrection to orbital rate
Account for orbit precession
Account for J2
harmonic in radial, along-track, & cross-track
![Page 26: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/26.jpg)
26
26
GPS Ephemeris Message Representation URE
![Page 27: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/27.jpg)
27
27
LEO Fit Interval to Match GPS URE Performance
![Page 28: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/28.jpg)
28
Orbit Determination?
![Page 29: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/29.jpg)
29
Ground Station Constraints
![Page 30: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/30.jpg)
30
Ground Station + Crosslink Constraints
![Page 31: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/31.jpg)
31
Use GPS Above
![Page 32: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/32.jpg)
32
32
Total Ionizing Radiation DoseFor a 5 Year Mission with 5 mm Aluminum Shielding
Failure of COTS Parts
![Page 33: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/33.jpg)
33
33
Total Ionizing Radiation DoseFor a 5 Year Mission with 5 mm Aluminum Shielding
‘Careful COTS’ Design1
[1] D. Sinclair and J. Dyer, "Radiation Effects and COTS Parts in SmallSats," in Proceedings of the 27th AIAA/USU Conference on Small Satellites, Logan, UT, 2013.[2] P. C. M. Stanczyk, M. Silveira, "Space CSAC: Chip- Scale Atomic Clock for Low Earth Orbit Applications," presented at the Proceedings of the 45th Annual Precise Time and Time Interval Systems and Applications Meeting, Bellevue, WA, 2013.
Targ
et A
ltitu
des
CSAC2
![Page 34: Leveraging Commercial Broadband LEO …web.stanford.edu/group/scpnt/gpslab/website_files/LEO...Leveraging Commercial Broadband LEO Constellations for Navigation Tyler Reid, Andrew](https://reader033.vdocuments.net/reader033/viewer/2022053017/5f1c03812618de53362cab68/html5/thumbnails/34.jpg)
Conclusions
• Navigation from LEO:
– Strength in numbers: more satellites and better geometry allows looser constraints on the URE (Orbit + Clock).
– Less harsh radiation environment allows for ‘careful’ COTS design.
• Potential Benefits:
– Closer satellites can mean stronger signals and resistance to jamming.
– Geometric diversity: LEOs move across the sky faster than MEOs, giving some multipath rejection.
– Constellation is more robust to single satellite failures.
34