Submillimeter and millimeter debris in LEO Mike Gruntman [email protected]
Optical detection of submillimeter and millimeter debris in LEO
Mike Gruntman Department of Astronautical Engineering University of Southern California
Acta Astronautica, Future In-Space Operations (FISO) Seminar v. 105, 156-170, 2014 February 25, 2015 10.1016/j.actaastro.2014.08.022
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Orbital Detection of ... Debris in LEO
• orbital debris in LEO
• observational gap and limitations of current techniques
• LODE (Local Orbital Debris Environment) concept photon-counting time-tagging imaging sensor debris detection
• LODE example and performance characteristics antic ipa te d annua l num ber of d eb ri s event s/d et ecti ons
• mission and CONOPS
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• range from tiny (10 m) to very Large debris: > 7–10 cm (3″–4″) l(10)large (10 m) tracked and cataloged by U.S. SSN • pose threat to spacecraft ~ 19,000 loss of spacecraft active satellites can avoid collisions ddtidlfdegradation and loss of (in principle) by maneuvering capabilities (incl. mission ending) Space Fence will improve tracking of subsystems and payloads capabilities
Small debris: < 5 cm (2″) U.S. National Space Policy, 2010 characterized statistically “increase understanding of the cannot be avoided by maneuvers current and future debris environment” 1 mm – 10 cm: estimated >107 < 1mm: estimated >1012
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< 0.1 mm Observational Gap • can be experimentally characterized by bringing exposed surfaces back to Earth from orbit (LDEF, SMM, EURECA, Space Shuttle) Models (()ORDEM and MASTER) disagree (order of magnitude) in > 5 cm the 0.1–10 mm range • tracked/cataloged by radar
Focus of this work: 0.1 – 10 mm submillimeter (0.1 – 1.0 mm) and millimeter (1 – 10 mm) debris • too small to be detected by radar or optically • too few to be measured by studying exposed surfaces one hthas to rel y on mod dlieling
damage to spacecraft and payloads ranges from surface degradation to loss of spacecraft or its components and payloads Figure: Krisko et al., IAC-14-A6.2.8, 2014
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ditfdbi>1density of debris > 1 mm atmospheric drag effectively removes debris below 600 km • 1-mm sphere at 400-km altitude reenters the atmosphere within a couple weeks
debris accumulate above 700 km • solar radiation pressure could decrease lifetime of large area- to-mass ratio debris • maximum density at ~ 800 km
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RdRadar an dOtilLiittid Optical Limitations Radar limitations • radar detection ~R-4 NASA Haystack and Goldstone • radar cross section (RCS) • can detect debris down to several mm at RCS ≈ area (d2) for d > 3 altitudes of 400 km • RCS drops precipitously with decreasing Haystack and Haystack Auxiliary (HAX) size for d < (1/3) (Rayleigh scattering) • demonstrated detection up to 800 km • most radars operate in S band ( = 6–15 cm) and X band ( ≈ 3 cm) • atmospheric absorption fundamentally German TIRA radar limits increase of radar frequencies • detected 1–2 cm debris at altitudes up beyond X band to 1000 km
Optical observations • a number of feasibility studies for observing • ground- and space-based telescopes millimeter and (primarily) centimeter size primarily observe large GEO objects debris in LEO by space-based sensors • space-based optical sensors observe • all based on CCDs in focal plane large objects in LEO (e.g., MSX) • nobody looked at submillimeter debris
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Observation-validated models of Local Orbital Debris Environment (LODE) dbidebris env ironmen t essen tilftial for • to measure debris near satellite orbit optimal design and safe operations of satellites • based on passive optical photon-counting time-tagging imaging system models disagg(ree (0.1–10 mm) •a way tlto close thbthe observa tiltional gap even if they were in agreement, important to validate
NASA Handbook 9719.4, 2008 This work: “From the safety and the satellite operations perspective, there is top-level an immediate need for a large feasibility and dedicated meteoroid and study orbital debris sensor to monitor (unfunded) and update the populations between 0. 1 and 10mm1.0 mm.” Acta Astronautica v. 105, 156-170, 2014
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focal plane detector of a small telescope • photon-counting time-tagging imaging system (position-sensitive detector based on microchannel plates – PSD based on MCP) • essentially different from frame detectors (CCDs)
PSDs used since 1970s • laboratory and space MG: • open type (electrons, ions, EUV, X-rays) and review sealed with photocathode (optical) article in major • numerous space instruments (plasma and physics energgpetic particle anal y;yzers; EUV and X-ray journal spectrometers and imagers) in 1984 • optical: ground-based telescopes (very few) • optical: currently operational in two instruments (COS an d STIS) on Hu bble S pace T el escope
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Siegmund et al., • incident particle (photon) converted into an SPIE-8033, 2001 avalh(lanche (106–108)fl) of elec trons • different types of readout schemes • determine: coordinates (x,y) and detection time (t) of each registered photon in real time • image built up (accumulated) in computer memory
• sensitive area: 20×20 mm to 100×100 mm • spatial resolution: up to 2000×2000 pixels • time (tagging) resolution: ~1 ns • max count rate (total): up to 106 s–1 • max count rate (point source): 10–100 s–1
PSDs essentially differ from frame detectors (CCDs)
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Prior studies of optical space-based LODE debris detection sensors fdbidttifor debris detection • debris passage across FOV forms • CCD in focal plane “3D debris trajectory” in (the focal • debris passage across FOV during a plane plus time) – (x,y,t) 3D space frame accumulation time interval results • requires detection of only several in a streak across a pattern of fixed photons to extract the rare event stars and diffuse background disadvantage: smaller photon detection •forms “2D debris trajectory” in focal efficiency than by CCDs plane – (x,y) 2D space • significantly smaller (than for CCD- • 20 or more photons are needed for based frame detector) number of signal above noise in a single CCD pixel debris-reflected photons should • reliable detection of a rare streak enter the sensor higher sensitivity requires multiple lightened-up pixels opens a way for detecting smaller • at least a few hundred debris- (submillimeter) debris reflected photons should enter the • MCP-based PSDs have been never sensor considered for detection of small debris
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Siegmund et al., DtDetec tion o fDbif Debris SPIE-8033, 2001
• bright stars: Phot o- must be avoided (small fraction of the sky) cathode (S-20) • PSD intrinsic noise: significantly smaller efficiency than diffuse background count rate
• sensor geometitric f act or ( 0×0)li) lim itdbited by sky light background
sensor sppgectral range assume ((psimplified ) • visible: 400–850 nm • antisolar pointing light background (e.g., sun-synchronous dawn-dusk orbit) • Zodiacal light • velocity of debris V0 = 10 km/sec normalifthFOVl crossing of the sensor FOV • integrated starlight of unresolved stars • isotropic (2) scattering of solar light by • diffuse galactic light debris with albedo = 0.15 • typical background intensity: • M debris-scattered photons to be 2 500 S10S ≈ 21 mag/arcsec ≈ 8.0 kR registered for debris event detection
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DtDetec tion o fDbif Debris Maximum distance hM for debris (size a) FOV crossing detection
Effective debris
detection area S(a) 0
a – debris diameter
V0 – debris velocity – debris albedo
d0 – sensor aperture diameter – photon detection efficiency
CM – maximum count rate
f0 – sky diffuse background A passage of an object larger in size and/or FS – solar photon flux closer to the sensor would result in a M – number of debris-scattered larger average number of registered photons photons and consequent event detection
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LODE E xampl e d0 = 6 cm (sensor aperture diameter) 4 –1 CM = 10 s (maximum count rate)
–6 0 = 5.35×10 sr (solid angle)
0 = 0.15º (plane angle) M minimal number of debris-reflected photons to be registered fOfor FOV crossing by a debris) mV = 7.6 and brighter to be avoided
necessary to determine 25,000 stars a probability that random background 1.1% of the sky photons produce a pattern of registered photons indistinguishable form a true debris detection PSD (in the focal plane) 15–25 mm (diameter) 128×128 pixels (resolution)
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Mini mal N umb er of R egi st ered Ph ot ons M
example: it takes t= 1 ms for a debris to cross the selected FOV at the h = 3.8 km distance
One would consider photons registered (accumulated) during such a time interval of (t = 1 ms) for search of events of debris passage at this distance (h) or closer t, ms
1 false event per year
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Maximum Distance and Detection Area
actually, effective maximum detection distance and effective detection areas are largg(er (a factor of ~2 for area) because of the Poissonian nature of detected photons 1 false event per year size 0.15 mm 0.3 mm 1.0 mm 3.0 mm 10 mm M 4 4 5 6 7
hM 15.6 m 62 m 0.55 km 4.2 km 40 km t 0.004 ms 0.016 ms 0.14 ms 1.1 ms 10 ms S032mS 0.32 m2 51m5.1 m2 400 m2 0. 023 km2 20km2.0 km2
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1 mm at 0. 55 km 3mmat42km3 mm at 4.2 km 10 mm at 40 km LODE FOV Crossing by Debris
blue dots bkbackground photons
red dots debris reflected
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Orbit AlNbfDbiEtAnnual Number of Debris Events altitude 800 km flux density detection rate –1 ilitiinclination per 0. 1-mm bin , m2 yr –1 per 0. 1-mm bin , yr 98.5º
MASTER predicts fewer debris than ORDEM
total annual number (0.2 – 10.0 mm) – 1400 3.8 events per day submillimeter (0.2 – 1.0 mm) – 780 2.1 events per day (large) millimeter ( 6 – 10 mm) – 465 1.3 events per day
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Missi on and CONOPS
Instrument/experiment challenges Spacecraft and mission • detection of smallest debris closest to • small satellite or hosted payload the instrument • no major challenges to • capture of a burst of 10–15 photons spacecraft or CONOPS within 1 microsecond exception: high-data rate deadtime < 50 ns • raising the minimal debris size to Narrow-FOV LODE concept is 0.3 mm (()from 0.2 mm) will substantiall y complementary to radar (Haystack and relax the requirements to the detector HAX) and wide-FOV CCD-based optical instruments constrain uncertainties of • data rate 1 Mbps ≈ 1011 bit/day (raw) measurements byyq various techniques challenging for a small sat could be used for measuring debris in • real-time processing on board GEO, GTO, and dust in lunar environment • straightforward for short time intervals micrometeoroid fluxes (lldbi)(smallest debris) Thank you for your attention!
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About the Author
Mike Gruntman is Professor of Astronautics at the University of Southern California (USC); he is the founder of the USC Astronautics Program and served the founding chairman of the Department of Astronautical Engineering from 2004–2007. His research interests include astronautics, space physics and instrumentation, rocketry and propulsion, and satellite design and technologies. He is Co-I on current NASA missions IBEX and TWINS. Mike authored and co -authored 270 publications , including 85+ journal articles and book chapters and 3 books. He served on the editorial board of the journal Review of Scientific Instruments and on various government advisory panels. Mike teaches courses in spacecraft design (1100 graduate students during the lt10last 10 years ) an d spacecra ft propu liHlsion. He a lso teac hes s hthort courses (AIAA, ATI) to industry and government. Web site: astronauticsnow.com email: [email protected]
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