Hello all,
This might be slightly off topic, but I'm betting someone on this list can point me in the right direction. I'm looking for ways to track spacecraft that are not in Earth Orbit (NEO?...did I just invent another acronym?...probably not.). I'm trying to figure out ways to track man made space vehicles sent to places like the Moon, Mars, the Lagrange Points, and beyond. As I understand it, TLEs + SGP4 are not the appropriate model for things not in the vicinity of Earth. I'm hoping to find a similar technique though for looking up current orbital parameters for the Non-Earth satellites (like pulling TLEs from celestrak) in some kind of database that contains current elements for the spacecraft (NASA servers somewhere?), and then compute pointing angles from a location on earth so I can figure when and where to point an antenna to receive signals from these spacecraft.
I believe this may be relevant to those on this list that might be interested in tracking the Cube Quest Challenge amateur radio cubesat that will be sent to the moon in the near future. After the trans-lunar injection burn, the cubesat will be ejected from the deployer. I'd like to be able to track this satellite as it travels to the moon, and potentially help receive data from the bird's 10 GHz Downlink. But.......where do I point my antenna and when?
For spacecraft that are already orbiting the Moon, OK, easy enough. Unless the antenna has a very narrow beamwidth, I can use any 'ole EME tracking package to point my antenna 'at the moon' and with the beamwidths I'm working with, the satellite is probably in the main beam. But what about the initial journey to the moon? Also, for the CQC, the cubesat will not immediately enter Lunar orbit (that is where the 'Challenge' part comes in). So simply pointing at the Moon may not work reliably.
To get a little more detail......but hopefully not too much......
I like using a python module called 'pyephem' for all (well...most) things related to antenna pointing. This handy module works well with TLE formats for Earth orbiters, contains a built in database for objects in the solar system, and a decent number of 'fixed' celestial objects like stars. It has the ability to import new objects in the 'Xephem' format, for things like comets and other bodies. If possible I'd like to use this feature to track other space probes like the Lunar Reconnaissance Orbiter, various Mars missions, Satellites at Lagrange Points (ACE/DISCOVR), etc. etc.
Does anyone on the list have experience with this type of thing that they might be willing to share? I believe folks from AMSAT-DL participated in the ISEE-3 reboot mission, so how did they know when and where to point the Bochum antenna for this? Again, I'm looking for a technique that hopefully involves downloading current 'orbital parameters' of some standard format type (Like TLEs from celestrak, but for non Earth Orbiters) and then importing those parameters into pyephem (by possibly converting whatever gets downloaded into the 'Xephem' format?) in order to integrate this kind of capability into my current, python-based, tracking software. Does anyone know of any publicly available databases that store current orbital or tracking data for non-earth orbiting spacecraft? Any tutorials out there about the algorithms used to compute deep space spacecraft position from the orbital elements and thus the pointing angles (Like SGP4 + coordinate system math, but for non-earth orbiters)? Any software libraries anyone is familiar with for this (I prefer python, but am open to other languages)?
Any and all advice, thoughts, info, papers, links, etc. would be greatly appreciated.
Sincerely,
Zach, KJ4QLP