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1. Space Environment
Lecture 25 – Space Debris (Vol. 1)
Space debris measurements
Professor Hugh Lewis
SESA3038 Space Environment

2. Overview of lecture 25
• In this lecture we take a very high-level look at the key systems used to
gather data about space objects:
– Radar
– Optical telescopes
– [Note that I don’t cover Satellite Laser Ranging, but you can find out
more about this service here: https://ilrs.gsfc.nasa.gov/)
• We also look at how optical measurements can be used to help characterise
the objects in orbit, with a particular focus on the Starlink satellites
Space Environment – Space Debris (Vol. 1)

3. Radar measurements Space Environment – Space Debris (Vol. 1)
• Haystack Ultra-wideband Satellite
Imaging Radar (HUSIR)
• MIT Lincoln Laboratory
• 36.5 m steerable antenna
• W-band (92-100 GHz, 3 mm
wavelength)
• Principal mission is to identify and
characterise space objects in support of
space situational awareness
• Highest resolution space-object imaging
radar in the world
– Is able to track and image space objects in
GEO
https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv23i4.pdf
https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv24i4.pdf

4. NASA Haystack radar Space Environment – Space Debris (Vol. 1)
• Example image:

5. NASA Haystack radar Space Environment – Space Debris (Vol. 1)
Range and Range-Rate conversion to altitude and inclination:
Assumes circular orbit
https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv23i4.pdf
https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/odqnv24i4.pdf

6. Optical measurements Space Environment – Space Debris (Vol. 1)
• Used primarily for geosynchronous orbit
(GEO):
• Measure sunlight reflected by debris
• Limits when measurements can be made:
– Telescope is in darkness (night)
– Space-object is in sunlight
– Cloud-free skies
– Only relatively short periods when
these conditions are met in LEO
– Relatively long periods when these
conditions are met in GEO
– Relatively few locations on Earth
– (high altitude, favourable weather)
https://orbitaldebris.jsc.nasa.gov/measurements/optical.html
Fast-tracking Eugene Stansbery Meter Class
Autonomous Telescope (MCAT) on Ascension
Island

7. Space Environment – Space Debris (Vol. 1)
MMT
• Multichannel Monitoring Telescope
• Also: Mini-MegaTORTORA
• Developed jointly by Kazan Federal University (Russia), Special Astrophysical
Observatory of the Russian Academy of Sciences and Parallax Ltd
• Main use: search for optical transients (GRB afterglow, nova, supernova, variable stars,
etc.)
http://astroguard.ru/satellites

8. Space Environment – Space Debris (Vol. 1)
MMT
• Multichannel Monitoring Telescope
• 10 channels (each can centre on different fields)
– Canon 71 mm objective + Neo sCMOS Andor 2560 × 2160 pixel sensor
• 900 square degrees coverage for the whole system
• 10 frames per second:
– 0.1 s exposure = 12m
– 10 s exposure (100 stacked frames) = 14.5m
– 1000 s exposure (10,000 stacked frames) = 17m
• 1 Gb per second, 60 Tb per night
• A few hundred detectable objects cross the system FOV each night
• Measurements are correlated with known orbital objects using public orbital data
• As of 22 February 2021: 316,753 separate tracks from 7981 satellites

9. Space Environment – Space Debris (Vol. 1)
MMT
• E.g. Starlink-1031
• 2019-074Z/NORAD44736, Launch date: 11 November 2019
• Track: 11 February 2020 at 02:24 UTC

10. Space Environment – Space Debris (Vol. 1)
Optical measurements
Insights: Starlink brightness

11. Recap of lecture 25
• In this lecture we took a very high-level look at the key systems used to
gather data about space objects:
– Radar, with a particular focus on the Haystack radar
– Optical telescopes
– We also looked at how optical measurements (in this case, from the
MMT) can be used to help characterise the objects in orbit, with a
particular focus on the Starlink satellites and the brightness challenges
they pose to optical astronomy
Space Environment – Space Debris (Vol. 1)

12. Activity
• You can visit the MMT website
and search for light-curve data
here:
• http://astroguard.ru/satellites
• See if you can find light-curve
data for Starlink satellites
deployed with and without the
new visors and compare the
brightness
Space Environment – Space Debris (Vol. 1)