JPL Horizons on-line solar system data and ephemeris computation service

Post by krisoft » Fri, Jan 03, 2025, 9:58 PM UTC

mturmon wrote: post #11

jvanderbot wrote: post #6

Earlier quoted context omitted.

Indeed, I've met many of them and worked with some of them. One of the main devs for this webapi project, who is a delight to work with, was just laid off sadly. Just for some additional context, the main library used by all these packages is SPICE, a C library written and maintained by JPL. https://naif.jpl.nasa.gov/naif/aboutspice.html It dates back to 1982, IIRC. And yeah, as mentioned you can still telnet in and…

> used by a ton of missions and spacecraft for determining sun up/down times, pointing angles for heavenly bodies, time and precise keeping, etc etc. Yes. My use case was/is determining pointing angles between a telescope at L2 and various nearby stars, to be sure it's not pointing anywhere near a bright body like a planet (around Sol) when it's expected to be observing exoplanets. There are a lot of diverse use case…

Post by mturmon » Sat, Jan 04, 2025, 7:26 AM UTC

aannex wrote: post #16

mturmon wrote: post #2

This group at JPL is the canonical source for solar system ephemeris, including planets and small bodies. The underlying models are numerically integrated equations of motion that I’m sure include all kinds of corrections, especially for bodies of great interest — such as Mars, or moons being considered for science visits. I used to use the python package “jplephem” to support ephemeris queries, but I understand that…

oh hey, I'm the developer of SpiceyPy. IIRC jplephem implements their own parsing of spk files and isn't a full implementation of the SPICE API. SpiceyPy simply wraps SPICE (via CSPICE).

Post by dard » Sun, Jan 05, 2025, 1:05 AM UTC

7373737373 wrote: post #24

dard wrote: post #15

Im a developer for the upcoming space telescope NEO Surveyor (Near Earth Object Surveyor). I actually work quite a bit with a number of people on the team up at JPL, Horizons is the canonical source for ephemeris information. Another vital part of the chain is the Minor Planet Center (MPC), which is where all observations of asteroids and comets are sent by the community. The MPC is the international authority for th…

Is there an explanation somewhere of how JPL knows/receives the latest satellite position data? I think I've read about maneuvers being sent in advance, but once a maneuver (or flyby) actually happens (which may result in deviations from the plan), how (fast) does the ephemeris data actually align with reality through measurement of the actual spacecraft position and speeds again?