Discover and read the best of Twitter Threads about #orbitaldebris2019
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Here is a thread-based version of my talk at #orbitaldebris2019 yesterday. I haven't been able to include everything, but I hope it gives you a sense of what I talked about (Image Credit: 'Gravity' Warner Bros. Pictures 2013) #spacedebris 
Only 10% of future traffic in LEO goes to altitudes >1000 km. In absolute terms, that is only 17 objects per year added to the population above 1000 km. With respect to the existing population, the peak spatial density (at 800 km) is 4 times higher than anywhere else (data: ESA)
Repeating the 2010-2017 launch traffic cycle with 90% PMD compliance & no explosions leads to what appears to be a fairly 'stable' population. The total no. objects increases at only 5 objects per year. Collision fragments are deposited at ever-slower rates. All looks good!
Alessandro Rossi from IFAC-CNR (again!) at #orbitaldebris2019 comparing collision probabilities associated with 'mega-constellations' and with intact derelict clusters in LEO.
To borrow an idea from the author Lauren Child, it’s the worry you hadn’t even thought to worry about that should worry you the most [from "Clarice Bean Don't Look Now" - an excellent read IMHO]. It's the cluster at 975 km that dominates the self-induced collision probability
That particular cluster has a substantially higher collision probability than a 'mega-constellation' when the background population is ignored. Given the large masses of the derelicts compared with the constellation satellites, the risk is also magnified.
Kamran Memon from @spacegovuk is talking about ORAC - Orbital Risk Assessment Capability. For UK people older than 40 you will recognise the missed opportunity to include an image of a plastic box with flashing lights #Blakes7 #orbitaldebris19 #spacedebris
Kamran also scores with another acronym: C++ High Level Astrodynamics Propagator (CHAPS), which is perfect for the @spacegovuk
Impressive range of models and approaches under development at the @spacegovuk to enable licensing and to support the #newspace community in the UK to achieve its ambitions in a responsible way #orbitaldebris2019
Jason Forshaw from @astroscale_ returns to #orbitaldebris2019 to talk about advocacy for global policy around #spacedebris removal [it's a shame that @cweeden couldn't make it!]
[Interesting to see the mass target for debris removal is 1000 kg. It's a nice, round number. Would be good to see some evidence showing that this is a good threshold]
Jason calls for more transparency with respect to the sharing of spacecraft anomalies, citing UN COPUOS LTS guidelines and noting that this is common practice in the aviation industry
Always a highly: Darren McKnight now talking about intact derelicts in LEO #orbitaldebris2019
If two SL-16s collide, we will still be able to get to and use LEO, but that event will reduce the lifetime of all satellites within about 300 km by 10% [okay, he has the attention of the audience immediately]
*always a HIGHLIGHT
I'm in the other parallel session now, at #orbitaldebris2019, listening to Hedley Stokes from PHS Space talking about updates to the ISO Standards (particularly 24113).
The option to re-orbit above LEO after end of mission, which appeared in the 2011 version of the standard, has been removed from the 2019 update [this is a good step - graveyards are not sustainable in the long-term]
Future work will need to address large constellations, amongst other things.
Alessandro is back for the second talk of the session (he is also co-chair, so a busy morning for him!) He is now talking about the challenges associated with use of low-thrust systems for collision avoidance in large constellations #orbitaldebris2019
What is the probability of a collision? How many collision avoidance manoeuvres (CAMs) are expected? Good questions to ask.
The simulation approach used the cube method [developed by Liou et al. 2003, NASA] as a pre-filter. Then a propagator is used to find the time of closest approach and the close approach geometry, for use with the CAM.
Alessandro Rossi from IFAC-CNR is the first speaker this morning, talking about orbital similarity functions to connect fragments to their 'parent' objects #orbitaldebris2019
Taking advantage of functions typically used to link meteor streams to asteroid families, such as the Minimum Orbit Intersection Distance (MOID)
Simulated fragmentation of a 1000 kg spacecraft using NASA standard breakup model and applied the algorithm to the fragments. Breakup time was estimated to within 1 day but there were large errors in the orbit estimated
.@braunspace from @esa space debris office talking about the Space Safety Programme at #orbitaldebris2019
The talk is at a fairly Hugh level, so not many details of the underlying engineering solutions, but some interesting points emerging. E.g. desire to bring laser ranging into collision risk management to reduce orbit uncertainty
Environmental capacity is another focus of the programme. ESA aiming to understand what population can be maintained for a "stable environment" [but seemed to use a non-stable solution to illustrate this]
Now it's Jason Forshaw talking about the ELSA-D mission and the key business markets for @astroscale_ #orbitaldebris2019
ELSA-d is the world's first commercial mission to demonstrate technologies for #spacedebris removal. Jason identifies the growing interest world-wide in debris removal.
ELSA-d consists of a 120 kg servicer and a 20 kg client spacecraft. Full phases of operation for end-of-life servicing will be demonstrated, including capture without tumbling, capture with tumbling, and removal.
Christophe Bonnal from @CNES now talking about Just-in-time collision avoidance for large derelict #spacedebris using clouds of particles #orbitaldebris2019
[I recall this exact concept being presented by Darren McKnight during the joint NASA-DARPA workshop in Chantilly in 2009. Will there be anything new here?]
Just need a delta-V of 3.5 mm/s along velocity vector to induce a miss distance of 1 km over 24 hours for an object of 100 kg [I think]. Also needs very accurate orbit data
Ian Dargin from Ironstar Engineering presenting PRRISM at #orbitaldebris2019 - a method for directing solar wind to remove small #spacedebris without needing to be in the same orbit.
PRRISM redirects solar plasma through the polar cusps to create an intercept solution for debris in polar orbit
PRRISM would be located at 10 Earth radii [not sure how it would be able to target small debris from that distance - maybe that will be addressed later in the talk]
First up this morning is Anne Bennett from CCAR, now talking about identifying and assessing debris strikes in NASA spacecraft telemetry #orbitaldebris2019 #spacedebris
The work uses changes in spacecraft angular momentum. The spacecraft corrects for the torque resulting from an impact and the delta-H is detected and used to identify a strike
Need to filter out anything that is not a debris strike (slews, thruster firings) and any gradual changes in angular momentum
Arly Black from @PurdueUnivNews now talking about a study looking at dragsail systems for de-orbit and targeted re-entry #orbitaldebris2019
Arly looked at how Cd is affected by altitude [it wasn't] and angle of attack of a flat sail [big effect]
MC analysis with GMAT showed a lower Cd than is typically assumed [~0.93 versus often used value of 2.2]
Michael Nicolls from @LeoLabs_Space talking about collision risk assessment for derelict object clusters in LEO #orbitaldebris2019
For the derelict cluster at 975 km altitude from March to October 2019: 1862 close approaches (CAs) < 1 km, 410 CAs < 500 m and 22 CAs < 100 m, with 6 events having Pc > 1/1000. Mean time between collisions is 25 years.
Example of one close approach from a derelict cluster: two objects with combined mass of 11,000 kg missing by 95 metres at 14 km/s [substantial debris generating potential]
Benjamin Bastida Virgili from @esa space debris office now talking about Collision Risk Estimation and Automated Mitigation (CREAM) #orbitaldebris2019
Aim is "to conduct safe and efficient collision avoidance manoeuvres without human intervention," reduce human effort, reduce time between manoeuvre decision and time of closest approach, and reduce number of false alerts
Benjamin notes that @esa receive hundreds of alerts per week, with about 2 being actionable. These lead to one avoidance manoeuvre per spacecraft per year, on average
Listening to Don Kessler's talk in the opening plenary of #orbitaldebris2019 with PhD students from @UoSEngineering
Don talked about the early days of the @NASA Orbital Debris Program Office and concluded his talk with a call to the future generation of scientists and engineers to take on the global challenge of #SpaceDebris
He mentioned the need to improve our knowledge of #spacedebris in orbit in the 1 mm to 10 cm size range. He also asked whether the 25-year rule should be replaced with a requirement for active debris removal
