# What exactly is SL-24 DEB (2010-028D)?

After 3 months of work I've been able to spot satellite debris with my 20x80 binoculars for the first time. The object in question is SL-24 DEB (2010-028D).

According to the data presented in www.in-the-sky.org, the object seems to be a fragment of the SL-24 rocket body that placed the Picard satellite into orbit in 2010.

• What size does it have? The fact that was magnitude 5.3 impresses me (it has to be a large chunk of the rocket, right?).

• When the break-up happened? Is there any available information about the event somewhere?

• This debris is the result of a collision, an explosion or something else?

In general, it is impossible to know for sure, but we can do some detective work. My two go to web sites: https://www.space-track.org -- Catalog of all space objects kept by USAF/JSPOC https://planet4589.org -- Jonathan McDowell's amazing catalog of all things space

AS you point out 2010-028* is the international designator for all the objects related to the launch of the Picard satellite on 15 June 2010. Space-Track has 6 listed (A-F). The international Designator is always associated with the launch itself, regardless of when the object became a standalone object (e.g. from a deployment or break up). We can conclusively say that all six objects are related, at least according to JSPOC. You will notice that objects A-E have consecutive NORAD catalog numbers (36598-36602) that means they were cataloged at around the same time. And in this case "same time" likely means the same day, since object 36603 was a Soyuz that launched that same day. So the debris objects, if they are debris, likely came off the rocket, and since there are only two, they are unlikely to be from a breakup. Object F has a catalog number of 36827 which implies it was deployed about two months later

Unfortunately the JSPOC doesn't spend a lot of time assessing what is what, and since most 3rd party sites like in-the-sky get their data from JSPOC, you end up with totally not helpful names like SL-24 DEB. In this case I believe SL-24 stands for "Space Launch 24" a Western designator for the Russian/Ukranian Dnepr rocket.

Luckily Jonathan is a little more thorough in his research and identifies the following in his version of the satellite catalog:

S036598 2010-028A      Picard                                   Picard
S036599 2010-028B      PRISMA-Mango                             Prisma MAIN
S036600 2010-028C      R-36M2 DS                                R-36M2 DS
S036601 2010-028D      Gazodinamicheskiy Ekran                  GDS (Gas dynamic shield)
S036602 2010-028E      Dnepr Platform A/Fairing                 -
S036827 2010-028F      PRISMA-Tango                             Prisma TARGET


Here Jonathan looks to have done some additional research. Objects A is Picard. Object B is PRISMA, which consisted of two satellites that launched attached to each other and separated on 12 August 2010 into its two independent components dubbed Mango (which kept the original designator and catalog ID) and Tango, which gained the F designator. This all matches what is in Space-Track.

Object C is the third stage of the rocket. R-36M2 is the stage name. R36 was the Soviet designator for the original ICBM that Dnepr is derived from.

That leaves us with objects D and E which are labeled as debris by Space-Track. 8 other entries in Jonathan's catalog have the word "Gazodinamicheskiy" all associated with Dnepr rockets.

Some Google searches on "Gas Dynamic Shield" led me to this Spaceflight 101 web page. It states that the shield is "element of the payload stack, protecting the satellite after separation of the payload fairing, especially during the operation of the third stage that fires its engines backward, pulling the stack into orbit"

Which means I leaned something new. I found this interesting tidbit on NASASpaceflight.com: "Originally designed to fine-tune the trajectories of multiple independently-targeted warheads, the unit has its engines mounted facing forwards." So that explains the heritage of the strange "backwards" configuration of the third stage. And the need for the mysterious debris that started your inquiry.

For this launch Dnepr used a small type 3.4.1 fairing which appears to be around 5 meters long. I would expect the shield to be slightly smaller than that, so your object is probably 4-4.5 meters. I couldn't find any pictures that conclusively would tell me the color of the gas shield.

• a fine bit of space detective work! – uhoh Dec 9 '19 at 17:56
• That's an amazing job. I'm very gratefull that people like you are around here to explain things step by step. This object is interesting because according to Sven Grahn the Gas Dynamic Shield is the 2010-028E object, while 2010-028D is considered to be an "Adapter for Picard". What is the most reasonable choice here? And what is "an adapter for Picard" supposed to mean? svengrahn.pp.se/trackind/Prisma/Prisma.htm#ObjectID – Swike Dec 9 '19 at 18:40
• My guess is that the "adapter" is the launch adapter which joins the satellite to the rocket. It usually stays attached to the rocket, although sometimes to the satellite, after the two separate. There may be ways to figure out which of the debris objects is what based on magnitude, spectrum, and orbital dynamics, but they are likely just educated guesses. So Grahn's identification may be accurate, but I put my money on McDowell just because he does this for every single launch. – Carlos N Dec 9 '19 at 23:36
• Perfect! Just to add something there is partial low resolution image of the GDS inside the Dneper head (the object in question) here: b14643.de/Spacerockets_1/East_Europe_3/Dnepr/Gallery/… And there is usefull information about the adapters here: snebulos.mit.edu/projects/reference/launch_vehicles/DNEPR/… – Swike Dec 10 '19 at 1:47