The lecture discusses space surveillance networks and space situational awareness. It introduces the US Space Surveillance Network, which tracks objects 10 cm and larger in low Earth orbit and 1 m and larger in geosynchronous orbit. Commercial networks like LeoLabs and ExoAnalytic Solutions are also discussed. Data from these networks is used for important services like conjunction predictions to ensure space safety. The next lecture will focus on systems used to measure and characterize space objects.

1. Space Environment
Lecture 24 – Space Debris (Vol. 1)
Space surveillance & situational awareness
Professor Hugh Lewis
SESA3038 Space Environment

2. Overview of lecture 24
• In this lecture we introduce the space surveillance network and look at how
data from this feeds into a variety of space situational awareness resources,
including Space-Track (the “official” source of orbital data from the SSN)
• We also look at a commercial space surveillance networks deployed by the
companies LeoLabs and ExoAnalytic Solutions
• We take a brief look at how data from these networks are being used to
provide important space situational awareness services, particularly
conjunction predictions which are vital for ongoing space safety
Space Environment – Space Debris (Vol. 1)

3. Space debris: topic overview Space Environment – Space Debris (Vol. 1)
• The space debris environment: update
• Space surveillance/measurement of space debris
• Impacts on space operations
• Modelling of space debris
• Environment/evolutionary modelling
• Impact modelling
• Breakup modelling
• Re-entry modelling
• On-ground risk modelling
• Clean Space
Volume 1 (Week 5)

4. Space Surveillance Network Space Environment – Space Debris (Vol. 1)
• The US Strategic Command (USSTRATCOM) uses the SSN to track the largest objects
in the near-Earth environment
• Objects approximately 10 cm and larger in low Earth orbit
• Objects approximately 1 m and larger in geosynchronous Earth orbit
• USSTRATCOM shares the data with the global community via Space Situational
Awareness (SSA) Sharing Agreements and the www.space-track.org website
• NASA and others use additional radars, telescopes, and in-situ measurements to
characterise objects too small to be tracked by the SSN, but large enough to threaten
human spaceflight and robotic missions
• Millimetre-sized debris represent the highest penetration risk to most operational
spacecraft in LEO

5. Space Surveillance Network Space Environment – Space Debris (Vol. 1)

6. Space Fence Space Environment – Space Debris (Vol. 1)
• Multistatic radar
• Multiple radar stations approximately along
the 33rd parallel across Continental US
– Three transmitter sites operating at 216.98
MHz
– Master transmitter at Lake Kickapoo,
Texas (768 kW radiated power
– Six receiving stations
• Originally used in conjunction with a
network of cameras that could see
basketball-sized objects at 25,000 miles
• Detected objects directly overhead up to
12,000 km
Ceased operation in 2013

7. New Space Fence Space Environment – Space Debris (Vol. 1)
• Gallium Nitride (GaN) powered S-band
ground-based radars
• Under construction at Kwajalein Atoll
in the Marshall Islands
• Selected locations and higher wave
frequency
– Will permit the detection of much
smaller microsatellites and debris
than current systems
– 10 times the number of objects
detected
– Simultaneous detection, tracking and
characterisation of objects
https://www.lockheedmartin.com/en-us/products/space-fence.html

8. Space-Track Space Environment – Space Debris (Vol. 1)
• https://www.space-track.org/auth/login
• Space situational awareness service
provided by US Space Force, 18th Space
Control Squadron
• Free to register and access the API:
• Orbital element sets (TLEs)
• Satellite Catalog
• Re-entry predictions
• Conjunction predictions

9. Celestrak Space Environment – Space Debris (Vol. 1)
• http://celestrak.com/
• Space situational awareness service
provided by T.S. Kelso
• Free to access :
• Orbit visualisation/propagation
• Orbital element sets (TLEs)
• Satellite Catalog
• Conjunction predictions (SOCRATES)
• Space weather data
• STK scenarios

10. LeoLabs Space Environment – Space Debris (Vol. 1)
• Commercial space situational
awareness services
• Phased array radars use a beam that can
be reoriented hundreds of times a
second (no mechanical slew
mechanisms required)
• Can track multiple objects
simultaneously
• Three radar sites:
– Poker Flat Incoherent Scatter Radar
(Fairbanks, Alaska)
– Midland Space Radar (Midland,
Texas)
– Kiwi Space Radar (New Zealand)
https://www.leolabs.space/
https://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=4412&context=smallsat

11. LeoLabs Data Platform Space Environment – Space Debris (Vol. 1)
• Offers data and analyses:
• Radar measurements
• Objects state estimations
• Object propagations
• Conjunction screening and alerts
– 3 million conjunctions < 100 km each day
– 800,000 conjunction messages per day
– Satellites can query the API and receive
conjunction information
– E.g. Starlink
https://www.hou.usra.edu/meetings/orbitaldebris2019/orbital2019paper/pdf/6096.pdf

12. LeoLabs Space Environment – Space Debris (Vol. 1)
https://twitter.com/leolabs_space/status/1222650724347252736
https://medium.com/@leolabs_space/the-iras-ggse-4-close-approach-a99de19c1ed9
• IRAS/GGSE 4 close approach 30 January 2020
• 47 metre predicted miss distance

13. ExoAnalytic Solutions Space Environment – Space Debris (Vol. 1)
https://exoanalytic.com/
• Space domain awareness solutions
• Global telescope network
• Independent space object catalog for high altitudes
(MEO, GEO, HEO)
• 10 million measurements per month
• Position and visual magnitude measurements
• Persistent observation/monitoring:
– Orbit determination
– Pattern of life analysis
– Manoeuvre characterization
– Light curve signature analysis

14. Space Environment – Space Debris (Vol. 1)
AstriaGraph
• Dr Moriba Jah, University of Texas - Austin
• TED Fellow
https://twitter.com/moribajah
https://en.wikipedia.org/wiki/Moriba_Jah

15. Space Environment – Space Debris (Vol. 1)
“Steely-Eyed Missile Man”

16. Space Environment – Space Debris (Vol. 1)
AstriaGraph
• Space Domain Awareness
• http://astria.tacc.utexas.edu/AstriaGraph/
• https://github.com/ut-astria/AstriaGraph
• https://www.scientificamerican.com/article/the-quest-to-conquer-earths-space-junk-problem/

17. Recap of lecture 24
• In this lecture we introduced the space surveillance network and very
briefly looked at how data from this feeds into a variety of space situational
awareness resources:
– Space-Track (the “official” source of orbital data from the SSN)
– Celestrak
• We also looked at a commercial space surveillance network deployed by
the company LeoLabs
• We took a brief, high-level look at how data from these networks are being
used to provide important space situational awareness services,
particularly conjunction predictions which are vital for ongoing space
safety
• In the next lecture we focus on the systems being used to measure and
characterise space objects
Space Environment – Space Debris (Vol. 1)

18. Activities
• Visit the LeoLabs website:
• https://www.youtube.com/ch
annel/UCM5tRph-
FDk5ZxAeIp090gQ
• Visit the AstriaGraph website:
• http://astria.tacc.utexas.edu/
AstriaGraph/
Space Environment – Space Debris (Vol. 1)