Linked Questions

11 votes
3 answers
3k views

How to calculate the planets and moons beyond Newtons's gravitational force?

The question Calculating the planets and moons based on Newtons's gravitational force was pretty much answered with two items: Use a reasonable ODE solver; at least RK4 (the classic Runge-Kutta ...
uhoh's user avatar
  • 149k
7 votes
3 answers
10k views

How to generate TLE file?

Subsequently to this answer: What is the way of generation of TLE file for a satellite? How to deal with BSTAR drag term, mean orbital elements, etc.? The generated TLE will be used as the input for ...
Tarlan Mammadzada's user avatar
20 votes
1 answer
6k views

How often does the ISS orbit align with the day/night terminator?

In the following image (coming from SAT-Flare) you can see the orbit of the ISS (in red) and the day/night terminator (in blue). The terminator separates night from day along the surface of the Earth. ...
Stu's user avatar
  • 5,928
17 votes
2 answers
3k views

Was Alexander Gerst the first man to have bare skin exposed to the vacuum of space and live?

On August 30, 2018, a hole was found in the Soyuz Orbital Module on the ISS. Astronaut Alexander Gerst initially plugged it with his thumb, meaning a part of his bare skin touched space. I can't find ...
PearsonArtPhoto's user avatar
  • 121k
8 votes
2 answers
2k views

Is SGP4 propagation necessarily more accurate near the epoch chosen for TLE generation?

This interesting answer includes a quote from Space-Track: From Space-Track.Org FAQ TLEs can contain future epochs. About 20 satellites are categorized as "multi-day objects" because ...
uhoh's user avatar
  • 149k
7 votes
2 answers
1k views

Physical meaning of perigee advance

I'm starting to study orbital perturbations and I can't find any physical explanation about the perigee advance (apsidal precession) when considering Earth oblateness effects. Can someone give a ...
Julio's user avatar
  • 1,732
5 votes
2 answers
2k views

How do SDP4's "Deep space" corrections to SGP4 account for the Sun's and Moon's gravity?

The Simplified Perturbations model SGP4 is used to calculate Earth satellite state vectors (position and velocity) using standard ephemeris data encoded as TLEs (Two Line Elements). According to ...
uhoh's user avatar
  • 149k
2 votes
2 answers
926 views

Ephemeris output from Skyfield

Is it possible to use Skyfield to propagate a TLE forwards and then output its ephemeris, rather than geometric x,y,z at some point in the future? I've worked through the examples in the API and may ...
Puffin's user avatar
  • 9,644
4 votes
2 answers
587 views

What is the reason for secondary oscillations in apogee and perigee plots for objects 41332 and 41333?

This answer provides quite interesting plots of apogee and perigee for objects 41332 and 41333. The primary (sine wave -like) oscillations are probably due to perturbations caused by potential ...
Sergiy Lenzion's user avatar
2 votes
1 answer
979 views

Equation for orbital period around oblate bodies, based on J2?

In this answer I point out that the period of items (ring particles, moons, spacecraft, etc.) around an oblate body will not scale exactly as $a^{3/2}$ because the closer you are to the planet, the ...
uhoh's user avatar
  • 149k
7 votes
1 answer
406 views

What is this perturbation effect called, and what would be an analytical expression for the resulting eccentricity oscillations?

In this answer I've generated some oscillations of eccentricity by being somewhat naughty and propagating a TLE for +/-250 days from epoch. I believe it's okay for the purposes of demonstrating gross ...
uhoh's user avatar
  • 149k
4 votes
1 answer
234 views

Do orbits change over a period of time, especially when the Star is not at the center (example: Didymos)?

Consider a celestial body, say the asteroid Didymos for example, with an elliptical orbit around the Sun. Now since the Sun has a huge gravitational pull and mainly because it is not at the center of ...
Amit Hiroji's user avatar
1 vote
2 answers
414 views

Yet another OSIRIS! Has the DLR/GOM Space test of the cubesat optical communications link happened yet?

Speaking of "all things OSIRIS" I just ran across the OSIRIS optical communications system for cubesats and smallsats. OSIRIS (Optical Space Infrared Downlink System) highly compact optical ...
uhoh's user avatar
  • 149k