logo Tools for asteroid astrometrists on this site


Supply astrometry (either upload a file or cut-and-paste into a text box), and Find_Orb will compute an orbit, residuals, and ephemerides. Note that the on-line version is a stripped-down version of the Find_Orb software.


Supply astrometry (either upload a file or cut-and-paste into a text box), and Sat_ID will list satellites in that area with similar motion. This won't identify every artificial satellite; new ones are occasionally found. But it's usually pretty good.

Also note that the page lists IDs for artsats that appeared on NEOCP.

TLEs for high-flying artificial satellites

I compute TLEs ( Two-Line Elements) for several artsats in high (multi-day) orbits, based on astrometry gathered for the artsats by asteroid observers. You get one file per object, containing TLEs for a given year or two. This page lets you get all TLEs available for a particular moment you specify.

NEOCP Summary

Lists all objects currently on the NEOCP, giving magnitudes, current uncertainty in the ephemeris position and what it'll be a day from now, MOIDs, etc. The idea is to help in figuring out which objects really ought to be followed up, which can be followed up later, and which ones are "lost".

GPS/GNSS satellite list

For a given date/time and MPC code, this will give you accurate positions for all visible GPS and other Global Navigation Satellite System (GNSS) sats. Really verifying that the time reported with your astrometry is actually the time the object was observed is extremely difficult; it's not enough just to sync your computer to NTP or GPS. Timing errors are rampant in astrometry. Navigation satellites have well-determined ephemerides and move fast (about 35" per second), making timing errors very obvious and easy to measure. Even a 1/10 second error will show up as a 3.5" difference in the object's position in your image.

Once you've picked out a good satellite (one at high elongation and well above your horizon), you can generate an ephemeris for a particular GPS/GNSS satellite, observe it, and compare the computed and observed positions. You can also upload your GPS/GNSS astrometry to get analysis of your timing and "cross-track" errors.

Click here for an overview on why you ought to check your timing this way, and how to go about it.

Recent (and non-recent) MPECs list

MPC maintains a list of the most recent MPECs. My index covers all of them, and gives you a little summary of orbital parameters and observers for each object.

Parallax constants to latitude/altitude

And vice versa. Also handles base-60 to decimal and conversions to/from Cartesian coordinates.


Supply astrometry (either upload a file or cut-and-paste into a text box), and AstCheck will list asteroids in that area moving with that motion. This is roughly similar to MPC's MPChecker (Minor Planet Checker), but it's somewhat faster and takes the object's motion into account, not just its position. That allows it to make identifications with some confidence even if the object is off prediction.

Customized ephemerides

Here, you don't have to supply astrometry. Just enter the object name (can be any MPC designation, or a name such as 'Icarus', or a current NEOCP designation), and it'll compute an ephemeris for your location.

Generate 'offset' records for spacecraft-based astrometry

For ground-based observations, we can just look up the observer's location. Given an observatory code, we can find the latitude/longitude/altitude. Spacecraft move; observations from (C49) STEREO-A, (C57) TESS, (250) Hubble, etc. have to be accompanied by a second 80-column record telling you where the spacecraft was when the observation was made. The formatting has to be exactly right, and generating these "second records" can be error-prone. The above page lets you enter/upload "first record" spacecraft observations and will return both records.

Lat/lon/alt data for MPC observatories

The MPC's list of observatory codes gives you the code, longitude, parallax constants, and observatory name. The list on this site adds latitude, altitude, and 'region' (usually a country, sometimes a smaller civil/geographic division), and links to G__gle™ and Bing® maps.

Radar astrometry

The MPC is not a reliable source of radar data. I believe their radar inputs are currently "broken", and probably won't be fixed until the transition to the new ADES format is complete. In the meantime, you can click here for all current publicly available radar astrometry in the traditional, 80-column format. (Which is fine. ADES is very important for optical data, but doesn't add much for radar.)

Source code

C/C++ source code for most of these projects, and a variety of other astronomy-related software.