Discover and read the best of Twitter Threads about #spacedebris

Most recents (24)

After 6 years in orbit, we say goodbye to @CopernicusEU #Sentinel1B and thank you to teams here at ESA’s #MissionControl, who for months have worked tirelessly to troubleshoot the issue that has now resulted in end of mission 👉…
As the first mission of the @CopernicusEU Programme, Sentinel-1 comprises two satellites orbiting 180 degrees apart, providing all-weather, day-and-night imagery of Earth’s surface, designed, built, launched and flown by @ESA.
The partner satellite, Sentinel-1A, remains healthy in orbit, continuing to deliver high-quality radar images for a multitude of applications.

Our focus is on fast-tracking the launch of Sentinel-1C.
Read 8 tweets
On Monday, for the first time, we performed a set of manoeuvres to avoid a high-risk collision w. #SpaceDebris created in the #Cosmos1408 anti-satellite test last year.

This was a difficult #CollisionAvoidance manoeuvre.👏👏to our #Sentinel1A Control Team & Space Debris Office
#CollisionAvoidance monitoring is unfortunately routine work at #MissionControl, and our teams are well-practiced in reacting to high-risk events.

This near head-on #collision was however unique; the situation evolved rapidly, was tricky to avoid, AND we had <24 hrs warning
Sentinal-1A, part of the @CopernicusEU Sentinel-1 radar observatory providing day-and-night images of Earth’s surface, had its orbit altered by 140 m in order to prevent collision with a debris fragment ~several cm in diameter

Read 7 tweets
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:…) and in an update on the website (here:…) [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
#US, #Russia and #China made up for 88 percent of space debris, India among the lowest contributors…

By @Krittiiii
There are 25,182 pieces of space debris in the lower earth orbits, within 2,000 kilometres (km) of earth’s surface, according to the latest issue of Orbital Debris Quarterly News published by #NASA’s Orbital Debris Program Office.

These 25,182 pieces of space debris, include 8,171 active and defunct spacecrafts and 17,011 objects categorised as “spent #rocket bodies and other cataloged debris” as of February 4 of 2022.

#SpaceDebris #NASA
Read 9 tweets
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.
Even with great surveillance and tracking in the future, and the most robust space traffic regulations, collision avoidance manoeuvres will be part of space operations. Avoidance manoeuvres are unavoidable.
Read 7 tweets
#USSPACECOM deputy cmdr, Lt Gen John Shaw at @ascendspace on Russian DA-ASAT test: We are still characterizing this event. We expect the debris will grow over time. #Perigee, #apogee event will widen. "It will become a threat that we will have to deal with." #ASAT #Russia
Shaw: This isnt' the beginning of such activity. #Russia conducted a similar test in April, though it didn't target a #satellite. Russia is showing "disregard of the sustainability of #space."
Shaw likens tracking objects in #space to book version of #JurassicPark: Scientists had automated sensors to track dinosaurs & algorithm to count the expected number of dinos. Problem is, it didn't account for the population of dinos rising. ...
Read 12 tweets
"...aware of a debris-generating event in outer space. We are actively working to characterize the debris field and will continue to ensure all space-faring nations have the information necessary to maneuver satellites if impacted," says @US_SpaceCom in a statement.
Earlier today, @Space_Station crew forced to take shelter in their spacecraft due to a "debris field" possibly intersecting with their orbit. This occurred amid reports #Russia had conducted an anti-satellite weapons test.
Read 13 tweets
(Thread) As if I couldn't cry more today, while searching his email to reconnect w/ him, I learned my fav @Cornell prof died 3 yrs ago. There're no words to describe how much he meant to me & how sad I feel I didn't get to say one last thank u & get his advice one last time. Image
@Cornell Dr Kelley literally was the reason I didn't quit Cornell. I went there thinking of becoming an #aerospace engineer. I loved space (still do) & I was determined to work in that field, in @NASA. My eyesight is bad & I'm short, so I knew being an astronaut was out of the Q. /2
I took my first Elec Eng class w/ him (EE101). 1st test, got D (or F?). I went to a bathrm in Phillips Hall & cried my eyes out. My child dreams came to an end. I was too dumb for Cornell, NASA, astronomy. How stupid to dream so high! A nice lady saw me & said don't give up. 3/
Read 12 tweets
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 put this slide together using data from It shows the historical evolution of the orbital object population (as recorded in the public catalogue). The highlight statistic is that active spacecraft make up 20% of the current catalogue population [2/n]
Read 18 tweets
Livetweeting today's @SWFoundation Summit for Space Sustainability, using the hashtag #SWFSummit21
From @WaleedCandC: When looking at #ClimateChange the space-based EO perspective provides us:
-the global scale-view of climate change
-data to inform the implications of our actions
-tools to improve our models so we can better prepare for & mitigate changes. #SWFSummit21
Thelma Krug, Vice-Chair of the @IPCC_CH:
Remotely sensed data reduces our uncertainties in knowing our "energy budget" & "sea level budget," as well as better predict future conditions.

Remotely sensed data boosts re-analysis, homogeneity & continuity of datasets. #SWFSummit21
Read 60 tweets
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]
If we know the initial number of individuals in the population N(0) then this model allows us to estimate the number of individuals at any future time t. Here, r is the intrinsic rate of natural increase, which depends on the birth rate, b, and death rate, d [3/n]
Read 25 tweets
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.
The event today may have had a Pc between 0.02 & 0.2. In any case, the Pc was relatively small (compared to a Pc of 1) so a miss was the most likely outcome. For a chain reaction to occur a long & sustained sequence of collisions would need to take place.
Read 16 tweets
🇪🇺#EUSST contributes to protecting the safety & security of European economies, societies & citizens.

Our Operations Centres are monitoring a potential collision of two large, inactive #space objects. EU #SST estimates a probability above 1% that they may collide in two days👇
The two defunct objects are OPS 6182 (1978-042A), a meteorological #satellite🌧️🛰️ and rocket body🚀 SL-8 R/B (1981-041B). The network of EU #SST sensors📡 has been requested to observe the objects and provide additional measurements.
Stay tuned here for more updates.
⚠️Update: according to #EUSST's latest estimates using data from its surveillance radars, the close approach between #space objects SL-8 R/B & OPS 6182 expected by tomorrow will have a miss distance under 10m and a Scaled Probability of Collision over 20%! +updates to follow soon
Read 9 tweets
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.
The yearly rates based on this report are 675,451 close approaches < 5 km involving #Starlink (227,655 ignoring Starlink-on-Starlink conjunctions)
Read 9 tweets
ESA's #missioncontrol centre is preparing for the launch of #Sentinel6 on 10 Nov.

In particular, teams are rehearsing the 'Launch and Early Orbit Phase' – the riskiest period in the fledgling spacecraft's life

Find out more🛰️👉… Image
Like a bird hatching from the egg, this is the period in which a new spacecraft unfurls its solar arrays, wakes up to test its core functioning and manoeuvres into the correct path, all the while at its most vulnerable to the hazards of space.

#Sentinel6 Image
The @CopernicusEU #Sentinel6 Michael Freilich satellite will ensure the 'continuity of service’ of the Jason missions currently providing data on Earth’s changing oceans, but reaching the end of their lives. Image
Read 9 tweets
Another thread about sat collision probability 🛰️💥🛰️

This time let's talk about regulations, as the FCC has just solicited input about how to regulate collision risk

As we know, risk can be computed as = 1-(1-Pc)^N

where Pc = each sat's collision probability and N = # of sats
Now, you don't have to be a math expert to know which variable is most important in that equation. Yep, the exponent!

Say you've been offered X^Y dollars, where each variable is between 1-9 and you get to choose one of them. You'd choose Y every time! Who cares what X is? 💵💰💵
Surprisingly, the FCC has asked if they should regulate risk by only limiting Pc, or if they should also take into consideration the N part of the equation.

Isn't the math obvious? Why would anyone ignore the most important part of the equation?

Well, it makes it hard to comply
Read 6 tweets
I put this #orbit visualisation tool together in #Excel to help with teaching & I'm really pleased with how it turned out. 3D rendering & real-time/instant updates via a control panel without any complicated code. It should run on any PC or laptop. A few minor bugs to fix. ImageImage
P.S. I'm happy to share (*also for beta testing*) if anyone is interested. Please just send me a DM with your email address. It's a 2 MB macro-enabled Excel spreadsheet (tagging the #spacedebris tweeps too)
P.P.S. My DMs are not open (sorry!) so we will need to follow each other if you would like to send me your contact email. Or you can find mine online...
Read 3 tweets
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)
Our models have two distinct roles: PREDICTION and UNDERSTANDING. Understanding can help us to design better models and gather more relevant data. Both of these roles are important in relation to #SST, #SpaceSafety and #SpaceSustainability (3/n)
Read 39 tweets
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 Graph showing daily close a...
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.
14.6% of all close approaches - about 1-in-7 - of the 37,910 events in the 31 August 2020 SOCRATES report involved Starlink. This proportion includes Starlink-on-Starlink close approaches.
Read 4 tweets
In this extract from the @SpaceX response to the @FCC there is a calculation that might be relevant if satellites were molecules in an ideal gas (or perhaps if addressing risks from small #spacedebris) but is not appropriate when considering large objects or constellations. Image
This highlights a lack of #spacedebris expertise & experience, and reliance on a model (DAS) that is not understood.
As the analysis of SOCRATES data has indicated, the reality is very, very different from what @SpaceX is expecting. Satellites are not randomly distributed around the Earth and are not travelling in random directions.
Read 3 tweets
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) Image
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).
I realise that I am quite likely comparing apples & oranges here, but that's also one of the points I am trying to make.
Read 5 tweets
In 2019 I presented a paper at the 1st International Orbital Debris Conference looking at implications of relocating satellites of a large constellation from high LEO altitudes to low LEO altitudes (…). Here's a thread on some new analysis #spacedebris 1/n
In my presentation I pointed out that relocating satellites to lower altitudes might solve long-term space debris issues but wouldn't be risk-free & could introduce problems related to space safety. Adding traffic to an already busy region could increase conjunction events (2/n)
Space systems at altitudes below 600 km are typically small satellites such as cubesats. Often these do not have a propulsion capability and so cannot implement collision avoidance manoeuvres. The figure shows recent launch activity & spatial density (data courtesy of @ESA) (3/n)
Read 24 tweets
Yesterday 15:53 UT, the #ISS had to make an emergency manoeuvre to dodge a piece of #spacedebris.
My analysis suggests it was object 27923 (1987-079AG), a piace of debris from a Proton rocket stage. It would have passed close to the ISS at 18:28:09 UT
@SSC_NL (corrected repost) Image
The nominal miss-distance would have been ~0.5 km at 18:28:09 UT, but that has a +- of at least 1 km.
This debris piece of the Proton rocket that launched Komsos 1883 in 1987 is of 'medium' size according to CSpOC ('medium' = RCS 01.-1.0 m^2)
*Kosmos, not 'komsos', grrrr!!!!!
Read 4 tweets
Excellent piece by @moribajah that highlights some of the key challenges to #SpaceSustainability & #spacedebris mitigation.
For many aspects of spaceflight we can test (verify) compliance with a set of requirements before the spacecraft is launched. Will the thermal control system work? Will the solar arrays deploy? For compliance with #spacedebris rules/requirements we have to wait until after launch
We don't yet have the systems or the data needed to do this accurately or consistently across near-Earth space, and we don't yet have the understanding to do this fairly, in a way that encourages compliance without creating obstacles to sustainable development. Work still to do.
Read 3 tweets

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