I've looked at Is Iridium launch object M a test satellite? and I don't understand what seems to have happened.

The Iridium launch produced 11 orbiting objects when only 10 Iridium satellites were launched. There was speculation that S2 had failed to de-orbit into the South Pacific as planned.

However looking at object M it has now changed orbit to an inclination of 89.9 degrees with an apogee of 868 km and perigee of 739 km. This is not an Iridium orbit so is this in fact a test satellite for the SpaceX constellation?

If so it would have been launched from inside the payload adapter after the Iridium satellites had been deployed.


  1. the letter 'I' is skipped because it can be confused with "1", thus 2017-003A, B, C, D, E, F, G, H, J, K are the SATCAN numbers of the ten Iridium communications satellites
  2. what (if anything) was or is 2017-003L?
  3. what (if anything) was or is 2017-003M?
  4. if you haven't already, go back and click on the objects link to see stuff in space.
  • 2
    $\begingroup$ The reddit post you linked includes this edit: "Interesting discussion but the consensus is that Object 2017-03M (aka 2017-03L) was never part of the Iridium constellation but was a piece of debris from a true polar launch (89.9 degrees inclination) that was misidentified as being in an orbit of inclination 86.66 degrees. Apparently this is not unusual." Are you just posting in the hope that someone has more information than this? $\endgroup$
    – Bear
    Commented Feb 6, 2017 at 16:41
  • $\begingroup$ @Bear are you just asking in the hope that I'll say yes, or that I'll say no? It's been almost five years now, perhaps the consensus has changed, or solidified, or perhaps there's an official statement. There's nothing that says a Stack Exchange question has to have an immediate answer possible. $\endgroup$
    – uhoh
    Commented Dec 23, 2021 at 14:06

2 Answers 2


The Joint Space Operations Center or JSpOC:

...is the organization responsible for performing all of the orbit determination activity necessary to maintain the US space catalogue.

During announced space launches and satellite deployment (and of course unannounced ones as well!) various space monitoring technologies including ground based radar and optical telescopes make a series of observations of space objects for the purposes of orbit determination. At some point if an object crosses some threshold of potential to be a new object, it is assigned a NORAD Catalog Number. If an observed object is later determined to be a known object, the identity assigned to the catalog number is updated. Thus one object can easily appear under more than one catalog number.

International designators are applied to identifiable components of a space launch or a space mission. The naming is getting more complex as components attach and leave the international space station, or are shuttled there then deployed to space at a later time (e.g. cubesats getting tossed out of an airlock).

In this case 2017-003 is the third launch of 2017 to be assigned an international designator.

While observing the deployment, eleven objects were observed in addition to the Falcon 9 2nd stage, and assigned NORAD catalog numbers 41917 through 41927, and the letters A, B, C, D, E, F, G, H, J, K and M were assigned to them. It is not clear why the letter 'L' was skipped, but the letter 'I' is always skipped because of a potential ambiguity - it can be confused with the digit '1'. 41917 through 41926 likely matched the 10 Iridium satellites in character, and were later identified as IRIDIUM 102, 103, 104, 105, 106, 108, 109, 111, 112, 114 (not in that order, see below) the satellites known to be in the F9 2nd stage payload.

However, the eleventh object, number 41927 was in question. It seems to have been given the international designator 2017-003M, but was also called 2017-003L. From here:

I've been in email contact with Dr T.S. Kelso, who runs Celestrak.com. The first thing he did is got the orbital information from Iridium and matched them up, so the Celestrak database now has the satellites named. He has changed Object M to Object L in his database, as he can see no reason, other than an input error, for the letter L to be missed. If it was left for the stage, then there would have also been a spare. Catalog ID as well. (emphasis added)

As for the 11th object:

  • In all likelihood, OBJECT L is some kind of upper stage, unless there were deployment mechanisms expected to be large enough to track. We don’t have any RCS data yet (and even that can be unreliable), so there is no way to know if this is something large like a rocket body or something else. All we can do is continue to monitor at this point.

Today I've done a search on the celestrak website: https://celestrak.org/satcat/search.asp and by playing around with the search input, including the text in the un-selected data field, I could get the chunk of catalog numbers that included the ROI. You can see that number 41927 has been identified, and there are mysteriously un-named catalog numbers immediately following.

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JSpOC's orbit determination and object identification is a long way from perfect, and particularly suffers when several objects are released into similar orbits, hence the temporary misidentification of an extra object associated with the launch. There was no such object. The 2nd stage reentry was normal.


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