ITU-R International Satellite Communication Symposium

Copyright © 2011 Boeing. All rights reserved.

Commercial Space Object Monitoring capabilities and their impact on the mitigation of Satellite Interference

Geneva, 13-14 June 2016Dr. Mark A. SkinnerThe Boeing Company

4411 The 25 Way NE, Ste. 350Albuquerque NM 87109 USA

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Commercial Space Object Monitoring & Satellite Interference

Paralleling (but lagging) the launch, ownership and operation of satellites, space object monitoring, long the sole domain of sophisticated governments, has now come to include the participation of significant civil and NGO entities. These new capabilities, identified as beneficial to the sustainable use of outer space [1], are now at a level of technical sophistication that allows them to positively contribute to the mitigation of satellite interference. Utilizing optical telescopes of modest size, these entities are able to monitor the positions and trajectories of objects in the GSO to sizes as small as one square meter, with measured uncertainties in the position of these objects to 10s of meters, on the order of the size of a modern communications satellite. These techniques can contribute to mitigation of satellite interference in several ways:

• Removal of satellite “longitude bias” via absolute stellar reference frame measurements allows GSO satellite cluster members to avoid adjacent satellite interference.

• Measurement and incorporation of perturbative natural forces, e.g., solar radiation pressure, allows more accurate conjunction analysis, further into the future, between GSO satellites and space debris and active satellites.

• Accurate measurement of satellite ephemeris via these optical techniques (which are now more accurate than traditional radio-frequency methods, e.g., dual-station ranging) allows greatly reduced uncertainties when employing dual-satellite geolocation methods to determine the location of terrestrial sources of satellite interference[2].

We describe the current state-of-the-art in commercial space object monitoring, and how it might be of interest to members of the ITU regarding satellite interference.[1] United Nations Committee on the Peaceful Uses of Outer Space, Report of the Scientific and Technical Subcommittee on its forty-ninth session, UN Doc A/AC.105/1001 (2012).[2] M.H. Chan, "Application of a Dual Satellite Geolocation System on locating sweeping interference,” World Academy of Science, Engineering and Technology, Vol: 6, 2012-09-21

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Trends in Space leading to increased satellite interference

Movement from handful of space actors to much larger number, with more wanting to join: Bi-lateral -> Multi-lateralGovernment-> Commercial/Non-state actors“Big Sky” mindset -> Growing realization of congestednature of near-spaceExpensive/Big -> Cheaper/Small = More StuffProliferation of both space objects as well as space actors (especially non-traditional) creates a challenge EDSN CubeSat Swarm – NASA image

http://www.nasa.gov/content/what-are-smallsats-and-cubesats

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GSO space objects can be monitored from the ground

Geostationary Satellites. Photograph was taken on Kitt Peak in Arizona (lat=31.95°, long=248.5°), 20 Mar 2007, 2:30-11:00 UT. Camera was fixed and spanned 232.5° to 266.5° east longitude along the celestial equator. Setting was f/6.3; focal length=80 mm; film: Ektachrome 100 G.

Photo by Bill Livingston, National Solar Observatory. Used by permission.

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The long-term sustainable use of outer space is an area of active international discussion…

• UN COPUOS Scientific & Technical Subcommittee

» Long-term sustainable use of outer space Working Group

– "Guidelines & Best practices”– New “Space Events” Expert Group

» Space Object monitoring encouraged for enhanced long-term sustainable use of outer space

– TCBMs– Safety of Flight– Interference-free space operations

UN, Vienna International Center, Committee on the PeacefulUses of Outer Space (COPUOS).Photo by the author.

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Satellite Interference• Interference types

» Adjacent satellite interference– Close satellite orbital spacing or beam footprint overlap

» Space Environment satellite interference– Dead/drifting satellites and space debris: possible collision

» RF satellite interference from terrestrial sources– Misaligned Uplink signals– Un/intentional Jamming

• How can space object monitoring help to mitigate satellite interference?

» Removal of Longitude Bias» Improved trajectory information for satellites and space debris» More precise orbits enhance Dual Satellite Geolocation

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What interferes with our satellites?

•Cluster neighbors•All with different longitude biases

• "Rogue” & drifting dead satellites •Orbital Debris

•10,000's objects, many un-cataloged•Terrestrial RF interference•Harsh space environment- aging•System malfunctions

Satellite

p+, O, UV, CME

1. Ortega, J., Quintana, F., Ybarra, G.,“Mechanisms and pyros subsystem for the METEOSAT second generation”, Space Mechanisms and Tribology, Proceedings of the 8th European Symposium, held 29 September - 1 October, 1999 in Toulouse, France. Edited by D. Danesy. European Space Agency, ESA-SP, 438, 1999, p.169

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Boeingimages

(Technical University of Braunschweig; used by permission)

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Commercial Space Object Monitoring?

Typical activities:• Positional monitoring

» RA & DEC (stellar reference system) of space objects

» Conjunction assessment of detected debris, drifters, etc.

• Space Object Verification• Command Verification • Anomaly Resolution• Change Detection

Enabled via ground-based space situational awareness (GBSSA): Utilize network of small, COTS terrestrial electro-optical (e/o) sensors (telescopes + digital cameras) to observe man-made space objects to derive useful information on them.

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Large, expensive telescope not required

*But need a sensitive CCD camera (happily, a Moore’s law device)

*

http://www.tmt.org/gallery/photo-illustrations

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40-cm aperture telescope adequate to see large number of stars and GSO satellites

• “Raw” image shows large FOV of E/O sensor.

• Identification of large number of stars allows accurate position determination

• Detection of other man-made space objects allows conjunction assessment

• Collected signatures allow object characterization Image by the author

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State-of-the-Art for space object position & velocity measurements

Optical telescope measurements give more accurate positions than 2-station ranging

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State-of-the-Art: positional uncertainties ~size of GSO satellite

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Radial, Intrack and Cross-track (RIC) Position Sigmas

RIC

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Radial, Intrack and Cross-track (RIC) Velocity Sigmas

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Radial, In-track and Cross-track (RIC) Position σ’s Radial, In-track and Cross-track (RIC) Velocity σ’s

Radial, In-track and Cross-track positional uncertainties from E/O measurements converge to 10’s of meters.

Results courtesy of Dr. Tom Kelecy, The Boeing Company

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Accurate measurements enable improved conjunction analysis

“Range” (yellow) is separation distance

Distance between satellite & space debris (“range”)(yellow curve) scale is on right

Zoomed “Range” (yellow) doesn’t get closer than ~150 km vs. ~10 km prediction

State-of-the-art measurements & processing offer prediction uncertainties not exceeding a few 100 meters after 3 days.

Results courtesy of Dr. Tom Kelecy, The Boeing Company

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Dual-Satellite Geolocation (DSG)• Locates interference using Time Difference of Arrival (TDOA)

as well as Frequency Difference of Arrive (FDOA)• Requires the use of two satellites and two ground terminals• Improved satellite orbits reduce error ellipse

» E/O space object monitoring can provide improved satellite orbits

Information courtesy Mr. Ray Andrade, The Boeing Co.

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Conclusion

• Commercial space object monitoring (“ground-based space situational awareness”) offers information that was previously only available from government SSA entities

• Commercial space object monitoring can produce positional and velocity measurements superior to current state-of-the-art RF techniques

» Measurement uncertainty ~size of GSO communications satellite» Detection down to ~1 m2 object size at GSO» No need to have cooperative space object for monitoring

• This capability mitigates satellite interference in three areas:» Longitude bias removal (eliminate beam footprint overlap)» Improved conjunction assessment between space objects (COLA)» Improved dual-satellite GEO-location (determine source of interference)

Accurate space object positional information, now available commercially, can mitigate harmful interference from RF and physical object sources