Hi I thought I would ask this to the group. I'm sure I will learn something from the discussion even if there is no clear answer.

And I'm just talking about pointing issues here. Photometric issues are another problem, however I think it's roughly as difficult as seeing Deimos. Tough but not impossible.

I'd like to track the Artemis I moon mission, but I'm not sure how best to do that with my ArgoNavis + ServoCat setup.
NASA indicates they will provide a file of ECI state vector coordinates for the mission time period. These should convert to RA/DEC with a little trig.
Tracking it as a satellite TLE probably isn't too good past geostationary orbit (?).
Using Goto to an RA/DEC a little ahead of the spacecraft and trying to catch it going by could be feasible.
On the way to the moon the position is changing around a couple arc minutes per time minute. That's hand trackable.
The orbit at the moon is big. It will get about 9 degrees from the moon, so that is best for observing but it's outside the SmartTrack 2.5 degree tolerance for lunar rate.

Faking up comet or asteroid orbital elements doesn't seem like a good fit to the physics (?).

If I could just send a stream of RA/DEC and have a continuous goto that tries to follow those coordinates that might be a solution.
I'm pretty comfortable talking meade protocol to the ArgoNavis on the serial port. I'm not at all clear on how to communicate with the ServoCat usb port.

Any thoughts?

Hi Dave,

Thanks for the interesting post and great to hear you are going to attempt to track Artemis with your scope.

TLI takes place very early in the mission, at 1 hour 33 minutes 21 seconds. So there won't be any orbit around the Earth to make the use of TLE (three line orbital elements) possible.

At first blush, doing the conversion from the state vectors they will announce to RA/Dec sounds like the go. Someone on the net may end up automating it.
NASA are saying the state vectors will be with respect the Earth-centered inertial coordinate frame J2000.
See https://www.tumblr.com/nasaorion/692871881822502912/how-to-use-data-from-nasas-arow-tweets

Don't forget to normalize the x,y,z position to the unit sphere.

Find the norm first :-
norm = sqrt(x * x + y * y + z * z);
Then :-
x = x/norm;
y = y/norm;
z - z/norm;

Find Right Ascension :-
ra = atan2(y, x);
Then put ra in the range of 0 to 2*PI and convert from radians to hh::mm:ss

Then compute Declination :-
rho = x * x + y * y;
dec= atan2(z, sqrt(rho));
Convert declination from radians to degrees.

Something like this anyway. It's Sunday afternoon here in Sydney and I might have missed something in this quick back of the napkin response.

Argo Navis has the MODE SETUP, SETUP SCRATCH feature where you can manually enter an RA/Dec.
It then appears under MODE CATALOG under SCRATCH OBJECTS.

I'd really be interested to hear if you have success observing it.

Hi Dave,

Further thoughts.
The state vector will be geocentric and so in addition to my above post, one would need to also do a conversion to apparent topocentric position.
Like the Moon itself, it's "close" and parallax is otherwise significant.

Unistellar might also publish RA/Dec positions for Artemis on their web site here. They have a blog page suggesting they will.
https://unistellaroptics.com/ephemeris/
Playing with it using the JWT telescope as a test target, I note the page gives a result you can expand that provides the RA/Dec for your location.

I would not be surprised if similar pages to this pop up on the net

Hi Gary,

Thanks for mentioning parallax. My head has been out in deep space the last couple of months....
Back of the envelope calculation indicates it IS quite significant - around five degrees for something 40,000 km out.
My dark site location is about 34N 96W.

This is what the NASA ephemeris sample data looks like. Units are km for the first 3 position fields and km/3 for the last 3 velocity fields.
Reference frame is indicated as EME2000 which I have read is J2000 which for amateurs like me is the same as ICRS. The data starts about three hours after the
planned launch which as you pointed out gets it past trans lunar insertion.
2022-11-14T08:26:41.501 -22860.680921756499 18950.962595768899 17214.405150885199 -4.30829161625250 1.04848534174026 1.25910529705675
2022-11-14T08:30:41.501 -23888.266839769502 19197.345308001200 17511.810803142700 -4.25527710167788 1.00521574996665 1.21971347462224
2022-11-14T08:34:41.501 -24903.378132270002 19433.699111876300 17800.067494609099 -4.20431538433048 0.96485957059368 1.18282127868860
2022-11-14T08:38:41.501 -25906.492666522699 19660.687786784300 18079.745751358700 -4.15528446641811 0.92712818047433 1.14818925722893

This is going to be interesting because the parallax will be changing as the earth rotates.
I also need to check what the specific windows are for reasonable visibility at my dark site.
I did spot check that the data does have some line of sight visibility and the moon is up at night.

Perhaps an alternate approach is put my observing site into the same coordinates as the artemis ephemeris as a function of time and
calculate altitude and azimuth angles giving myself a few minutes head start then use the mode->Alt Az to camp out at the right alt/az and try to catch it going by.
That might make sense if the Alt Az is a corrected site based alt az using the two star alignment.
It probably doesn't make sense if that is a scope Alt-Az that could still be off a bit due to non-level ground.

On the plus side this is making me move forward on something I have wanted to do for a while which is get a portable linux setup going.
I've now got a raspberry pi and a portable monitor running off a 12 v battery using only 5 watts. I have a feeling traditional planetarium
packages aren't going to help much with this. No reason they should - crewed moon missions haven't exactly been common the last 50 years.

Thanks for your suggestions.
-Dave

Hi Gary,

This may be the easy way to get the pointing information:
https://ssd.jpl.nasa.gov/horizons/app.html#/

And while they do not have a nominal Artemis ephemeris at present they do provide a notice that Artemis data will not be available before a time around TLI. (14 Nov 07:19 Z)
The site also can be used for the Webb telescope ,and the output can be customized to include apparent RA,DEC and Alt Az on a customizable time basis.
There is an input for the observer location, and I think the parallax is consistent with the RA,DEC. difference between regular and apparent for their Webb data.
It looks like a very workable format.

I played around with a couple of python libraries: skyfield and astropy. While interesting there is learning curve that's out of scope for next week.

Thanks for the helpful forum discussion. I'll post a follow-up on what happens one way or the other.
Dave

davefmccoy wrote:Hi Gary,

This may be the easy way to get the pointing information:
https://ssd.jpl.nasa.gov/horizons/app.html#/

Dave

Hi Dave.

This is perfect.

Select Ephemeris Type as "Observer Table".

Select Target Body: Artemis 1 (spacecraft) (Orion)

Select your Time Specification. You can even define it in 1 minutes steps.

The table will produce lines with dates and times along with RA and Dec in terms of ICRF. which is exactly what you are after.

An RA/Dec coordinate can be entered into the SETUP SCRATCH menu on Argo Navis as a scratch object and then you can go to MODE CATALOG, SCRATCH OBJECTS and Argo Navis will guide you to it.

In the header of the table it will tell you if there is a "Visual Interferer", namely the Moon, which makes sense as you are heading toward it.

Hi Gary,

The virtual telescope project in Europe has been trying to put a cloud-free telescopic view of Artemis on their web site recently.
https://www.virtualtelescope.eu/webtv/
Nov 21 3:30 UTC is another attempt from them happening about thirty minutes from when I am writing this.

The ephemeris for my location unfortunately had Artemis only above the horizon in daylight during this phase of the mission.
I'll see if the Virtual Telescope project can detect it.
Possibly I will try on the return trip if weather, orbits, etc work out literally "all the planets line up".

Keep looking up,
Dave McCoy

Hi Dave,

Thanks for the link.

Indeed, since we are between Last Quarter and New Moon, the best chance will be on the return leg when the Moon is risen at night.

Ted Molczan posted these visual magnitude estimates back in late August but they were based on a August 29th 2022 launch date.
They might still provide some rough estimate.

http://satobs.org/seesat/Aug-2022/0236.html

Over at the British Astronomical Association one enthusiast reported that "I detected the Israeli Beresheet lunar lander when approx 1/3rd of the way there and
have seen the Russian Spektr-R mission near apogee, but neither appeared near the Moon, so I am keen to give it a go – cloud permitting."