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Hugh Lewis Profile picture
@ProfHughLewis
Dec 11, 2019 • 5 tweets • 2 min read • Read on X
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
Jason mentions the positive work done by @spacegovuk in advocating for #spacedebris removal
Industry and government should strive to achieve greater success of post-mission disposal. Debris removal is still needed and can complement post-mission disposal

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More from @ProfHughLewis

Hugh Lewis Profile picture
May 15, 2023
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] Graph showing the cumulativ...
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] Graph showing the cumulativ...
Here, I looked at the manoeuvre estimates/reports in 6-monthly intervals, corresponding to the reporting periods used by SpaceX. Additionally, I added a prediction to the end of 2024 based on an exponential fit through 30 April 2023. [3/n] Graph showing the number of...
Read 6 tweets
Hugh Lewis Profile picture
Sep 15, 2022
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]
The justification provided by the @FCC is that "a shorter benchmark would promote a safer orbital debris environment." [3/n] Image
Read 31 tweets
Hugh Lewis Profile picture
Sep 14, 2022
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]
Here's the same data from [2/n] plotted with respect to the number of satellites in each constellation in orbit, clearly showing #SOCRATES predicts that #OneWeb satellites experience more close approaches (within 5 km) per satellite than the #Starlink satellites [3/n]
Read 13 tweets
Hugh Lewis Profile picture
Jul 5, 2022
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]
Chart showing frequency of conjunctions at different collisi
#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]
In addition, some #Starlink & #OneWeb satellites experience more conjunctions than others. Most satellites experience relatively few encounters but a few satellites are involved in a relatively large number (charts shows data for 7 days from 30 June 2022) [3/n] Chart showing the frequency that Starlink and OneWeb satelli
Read 8 tweets
Hugh Lewis Profile picture
Jul 4, 2022
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] Chart showing the average daily number of conjunctions withi
#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]
On 1 March 2019 #SOCRATES predicted ~3860 unique conjunctions within 5 km. On 30 June 2022 the corresponding number was ~10,160, an increase of ~160%. #Starlink accounted for ~2570 (25%) & #OneWeb accounted for ~1250 (12%) [3/n]
Read 14 tweets
Hugh Lewis Profile picture
Apr 27, 2022
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]
My focus has mostly been on understanding the implications relating to the choice of the probability threshold for collision avoidance manoeuvres. With the #SOCRATES #Starlink data now running across nearly 3 years we can gain some insights that may be useful [3/n]
Read 35 tweets

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