Welcome to this month's look at #Starlink conjunction risk mitigation manoeuvres. Through 30 April 2023, I estimate that Starlink satellites have made a total of > 45,000 manoeuvres to mitigate the risk of colliding with other space objects [1/n] A better relationship to consider is the one between the (cumulative) number of manoeuvres and the (cumulative) number of Starlink satellites launched. The growth is a non-linear function of the number of Starlink satellites [2/n]

I've been thinking about the new proposed @FCC "five-year rule" for #SpaceDebris mitigation & wanted to share some analysis & thoughts. Whilst I think the intentions are good I believe the implications of the change are poorly understood. Let me explain... [1/n] As @brianweeden's excellent thread explains, "The new proposed ruling would require all FCC licensed satellites that end their life in LEO to re-enter the atmosphere within 5 years, and ideally ASAP." [2/n]

https://twitter.com/brianweeden/status/1568232780386934792

Latest analysis for #Starlink & #OneWeb shows these two constellations accounted for 42% of all close approaches within 5 km predicted by #SOCRATES at the end of August, with Starlink alone accounting for 29%. [1/n] On average, #SOCRATES predicts that each #Starlink satellite will now experience 1 close approach within 5 km with a non-Starlink object every day, and each #OneWeb satellite will experience 3.4 close approaches with a non-OneWeb object every day. These rates are increasing [2/n]

A follow-on from yesterday's thread with a note about averages. In a #SOCRATES report from 30 June 2022 the average collision probability for each #Starlink conjunction was 3.7E-6 but the range of values can be broad (chart shows data since 2019) [1/n]

https://twitter.com/ProfHughLewis/status/1543986914004533252

#SOCRATES predicted some events with a collision probability > 1E-2 (1-in-100) & some with a probability < 1E-7 (1-in-10,000,000). The average value might seem to be almost negligible & you might think all conjunctions would be similar, but that's not the case [2/n]

Welcome to my (delayed) monthly analysis of @CelesTrak #SOCRATES conjunctions. Since 1 March 2019, SOCRATES has predicted about 9 million unique conjunctions within 5 km involving active or derelict payloads. This is a thread focused on those involving #OneWeb & #Starlink [1/n] #OneWeb payloads have accounted for ~500,000 unique conjunction predictions since 1 March 2019 (5.5% of all predictions made), while #Starlink payloads have accounted for ~1.1 million (12.5%) [2/n]

In advance of my monthly analysis of #Starlink conjunction data I wanted to share some additional analysis undertaken over the last few days. It's a work in progress but here's a thread looking a little deeper at the #SpaceX approach to #Starlink orbital space safety [1/n] #SpaceX provided some relatively detailed information about its approach in a briefing to the #FCC (here: ecfsapi.fcc.gov/file/108107102…) and in an update on the website (here: spacex.com/updates/index.…) [2/n]

Earlier this week Elon Musk set out his team's expectations for #Starlink satellites over the next 18 months. I thought I would use this month's #SOCRATES analysis to see what the Starlink team should expect in terms of conjunctions & manoeuvres over that period & beyond [1/n] Before I start, I'd like to offer my thanks to @planet4589 for creating a page on his website with data that enabled me to move forwards with a critical part of the analysis. Thanks also go to @TSKelso for ongoing support and provision of SOCRATES data via @CelesTrak [2/n]

Important and informative update from @SpaceX in response to widespread concerns about #SpaceSafety & #SpaceSustainability associated with #Starlink. Lots to unpack but worth investing time to do so (it's the Feb 22nd update entry btw) spacex.com/updates/ There's a strong focus on the collision avoidance capabilities of the #Starlink satellites rather than on the services that inform those capabilities. Ryan Hiles and co-authors presented a hugely valuable insight on this aspect at @amoscon last year amostech.com/TechnicalPaper…

Elon Musk told the Financial Times that "Tens of billions" of satellites can be accommodated in orbits close to Earth. Here's a thread looking at whether this is correct...
bbc.co.uk/news/business-… 1/ To investigate, I used the stability model developed by Don Kessler & Phillip Anz-Meador, which Phillip presented at the 3rd European Conference on Space Debris in 2001

Maybe I am overthinking this, but it appears to me that all the reporting of the conjunctions involving Starlink satellites & the Chinese Space Station is forgetting that close approaches & avoidance manoeuvres are a normal part of space traffic management. Even in environments with little to no debris (e.g. in Mars orbit) collision avoidance manoeuvres are performed. Perhaps not routinely, but they do occur.

Here's a thread containing the slides and thoughts I shared at today's @seradata space conference. I wasn't able to invest much time to prepare the talk, so some of the slides will look familiar to those attending April's ESA #SpaceDebris conference. Some are new [1/n] [alt text: talk title "The Space Debris Environment - Current Status and Evolution of the Risk"]

I think the #KesslerSyndrome is too often presented as a tipping point or a threshold we have yet to cross, so I wanted to use some aspects of my paper at the 8th European Conference on #SpaceDebris to explain why I think that is wrong [1/n] The starting point of my thinking was to look at how natural populations grow. The simple exponential model is a standard model that describes the growth of a single population [2/n]

I am seeing some ill-informed takes on today's near-miss in orbit so would like to offer some trajectory corrections if I may. Firstly, the chance that a single collision would trigger a catastrophic 'chain reaction' that would sweep through LEO is tiny. For every close pass involving catalogued objects in orbit we can estimate a collision probability, or Pc. The Pc is between 0 and 1. If it is 1 we can say that a collision is certain. If it is 0 then we can say that a miss is certain.

All of my work interactions are virtual at the moment, as I am sure many of yours are too. In this format I think it is even more difficult to be aware of an #InvisibleIllness or #InvisibleDisability so for #MEAwarenessHour I'd like to ask you to keep this in mind. It will be harder for you to see if someone is facing challenges so it's perhaps even more important than ever to be kind & considerate in all of your online work interactions.

It could be argued that many of the approaches to ensure sustainability identified in this (otherwise excellent infographic) are actually focused on ensuring spaceflight safety & IMHO there are some fundamental omissions, most importantly to do with how we think about the future

https://twitter.com/esaoperations/status/1379744043630989312

It's also not really correct to place large constellations into the category of trends that pose challenges to long-term sustainability (even though most might disagree with me). If we do so, then surely we must place all past, present & future space systems into this category.

In the last #SOCRATES report of 2020 #Starlink satellites accounted for 29.1% (1-in-3.4) of all 44,530 close approaches < 5 km recorded for the first week of January 2021 with a total Pc of 1.7% #SpaceDebris Ignoring Starlink-on-Starlink conjunctions the constellation satellites accounted for 9.8% of all close approaches < 5 km.

It's time for my (seemingly monthly) look at conjunctions involving #Starlink satellites, as predicted by celestrak.com/SOCRATES/. In this month's update I have corrected an error in the conjunction rates for June, July & August (I missed some conjunctions) (1/n) #SpaceSafety In the SOCRATES report from 30 September 2020, with just over 680 #Starlink satellites in orbit (v0.9 & v1.0), there were 6957 conjunctions < 5 km involving at least one #Starlink satellite (17.7% of all conjunctions in the SOCRATES report) for the 7 days ahead) (2/n)

For those asking, this visualisation is made up exclusively of a single Excel chart (2D scatter plot) that contains multiple series. Some of the data are plotted as lines without markers, some are plotted just with markers. Spin buttons provide real-time updates. I convert the Keplerian elements for the orbit to Cartesian coordinates and then project the 3D position onto a 2D plane (that is plotted). I do this for true anomaly values between 0 and 360 deg. to get the orbit.

Here is a thread-based version of my talk at the @AeroSociety conference on 'Safeguarding Earth's Space Environment' that I hope gets some key points across about modelling #spacedebris & how it can help to identify the data we need to understand #SpaceSustainability (1/n) Caveat: I use images as metaphors, to help with understanding of key concepts, so my slides have no words in them. (2/n)

Observations & model of daily count of close approaches in orbit involving #Starlink satellites from 1 October 2019 to 31 August 2020. Close approaches shown exclude Starlink-on-Starlink events for miss distances of < 5 km and < 1 km. Data from SOCRATES #spacedebris Over the period: Starlink satellites were deployed at a rate of 1.81 per day. Each Starlink satellite deployed in orbit adds 0.48 conjunctions per day < 5 km.

New response to @FCC by @SpaceX identifies probability of #Starlink collision with large #spacedebris is 8E-5. Single conjunction event < 0.5 km on 2 July with SL-3 R/B predicted by SOCRATES on 30 June 2020 had max. probability of 3.5E-5 (dilution thresh: 0.169) Another event in the same SOCRATES report predicted miss of 172 m on 30 June with 3CAT-2 & max. probability of 1.39E-4 (dilution threshold: 0.044).