6

For Python and TLE propagation using SGP4 one very handy option is https://rhodesmill.org/skyfield/ As you probably already know a TLE is a strange animal. It does not really contain proper orbital elements, but instead is engineered with one purpose; to be fed into SGP4 so that that will generate reasonable position information for at least a few days ...


5

Skimming CCSDS RECOMMENDED STANDARD FOR ORBIT DATA MESSAGES, it looks to me like three different message types are defined: Orbit Parameter Message (OPM), Orbit Mean Elements Message (OMM), and Orbit Ephemeris Message (OEM). OPM gives position and velocity and optionally "osculating Keplerian elements". It is "suited to exchanges that "do ...


4

Answering almost a year later... This was a particularly hard launch for JSPOC to track. The systems, processes, databases, etc are not well set up for a launch with a hundred+ objects. It looks like a year later, 43822 still shows up as Object BS, and there are several other equally unidentified objects: Object X (43779), Object BE (43810), and others. ...


4

I thought that the distance should be kept strictly constant... Not strictly, the satellites are allowed to orbit and the variation in the distance between them is one particularly sensitive measure of the variations in Earth's gravity field. This variation in distance is one key part of the raw data provided by the pair. As I show below, if you have two ...


4

A detective story, not an answer I pulled the historical TLEs for the ISS from Space-Track.org. On 16 May 2016, it experienced a rev rollover. The TLEs around the rollover have rev's 99,989, 99,992, 1, 6 I then pulled up the historical TLEs for Explorer 7 in the time frame you suggested around 21 Aug 2019 - 27 Aug 2019. It includes the two TLEs you ...


4

These are so called "Analyst" objects: Analyst objects are on-orbit objects that are tracked by the U.S. Space Surveillance Network (SSN) with insufficient fidelity for publication in the public satellite catalog (SATCAT). The lack of fidelity may be due to infrequent tracking, cross-tagging (observation association with closely-spaced objects), ...


3

When an object becomes "lost", we usually know most of the orbital information, including apogee, perigee, inclination and orbital period. Those are shown in the table. What's not known is where in that orbit the object is currently located. The reason for this is that the position over time is very sensitive to the initial values. As a simplified example, ...


3

While not directly "spaceflight" blockchain technology will be used in the aerospace industry very soon (if not already): for authenticity verification of components. Many aerospace components are very expensive, produced in low lot numbers, and are engineered to ridiculous toleranxes. Particularly in the aircraft industry, selling counterfeit parts or ...


2

Here's a paper that describes what I think you're trying to do with generating an estimated covariance matrix from historical data. Peterson, G.; Gist, R.; Oltrogge, D., “Covariance Generation for Space Objects Using Public Data”, Proceedings of the 11th Annual AAS/AIAA Space Flight Mechanics Meeting, Santa Barbara, CA; UNITED STATES; 11-15 Feb. 2001. pp. ...


2

In October I attended a talk on blockchain applications in the space industry at a conference. The speaker (someone from PWC Space Practice office) listed a couple possible use-cases. These are more extensively described in this white paper. Note that this is just a list of things the speaker talked about and I'm not expressing any opinion on the value of ...


2

Here is a sample Python script I modified from the example at Space-Track.org (requires registration of a free account). It looks for all SpaceLink satellites only (I plan to modify it to accept a list or dictionary with resident space object identifiers instead): # STTest.py (copyright 2019 by Andrew Stokes, original file named differently) # # Simple ...


2

The SGP4 propagator does not actually use the day of year (just time since epoch), thus a value beyond 366 is just fine. Some people may add some checks to a TLE to raise this as an error, but the propagator itself would see no problem in it. Also, if you want to see how much "time since epoch" is there between the TLE epoch and a given date, you might get ...


2

I received a definitive answer from an expert on TLEs. When the rev number goes above 99,999 you should simply drop the leftmost digit and write the remaining digits into the TLE. For example: Rev # Digits in line 2, columns 64-68 ------- ------------------------------- 100,000 00000 156,287 56287 395,468 95468


2

First, the SGP4 propagator is meant to propagate TLEs. He takes a TLE and a time since the TLE's epoch as inputs and outputs a position and a velocity. By selecting several times, you get a trajectory. In STK, if you have a trajectory generated by some other method, i.e. the TwoBody propagator or the HPOP propagator, then STK can estimate a TLE that would ...


1

As I mentioned in a comment, without source at the time... SATCAT numbers 70000-99999 (70'000s, 80'000s, and 90'000s) are "analyst objects". This article from The Space Review indicates that these ranges had special uses, from the very beginning of the SATCAT: When the SATCAT was first setup, all of the information was being kept in one large database ...


1

I can't answer you fully why Celestrak is wrong, but the correct number is 44972. It seems like this was updated in the other source. New objects are around 45000 right now, they shouldn't be much larger than that.


1

If you want a complete answer about how SGP4 (or SDP4) does it, you should read form the original source: The Space Track Report #3. For the actual theory behind, you should read the references by Hujsak and Hoots, for which I could not have access. During the description of SDP4 routines, it says: "At this point SDP4 calls the initialization section of ...


1

There were 5 servicing missions to HST: Servicing Mission 1 in December 1993 Servicing Mission 2 in February 1997 Servicing Mission 3A in December 1999 Servicing Mission 3B in March 2002 Servicing Mission 4 in May 2009 The decrease in tracking frequencies in your plot coincide with SM 3B and SM4. At the end of each mission HST was boosted up to a higher ...


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