Artemis

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  • #611999
    Grant Privett
    Participant

    As the US are due to send the Artemis mission to the Moon soon, does anyone know if TLEs or an ephemeris can be obtained for its position en route? I assume they will have been calculated for its anticipated launch window.

    It would be nice to see how close to the Moon it can be tracked with modern amateur OTAs and sensors.

    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.

    #612002
    Daryl Dobbs
    Participant

    A few people in America are asking the same question on a NASA forum, a couple of web links were suggested

    https://forum.nasaspaceflight.com/index.php?topic=56906.0

    Apparently the trajectory will be available on this site after launch
    https://ssd.jpl.nasa.gov/horizons/app.html#/

    People around here are eagerly following our local hero astronaut Shaun the Sheep who is taking a big step for lambkind

    • This reply was modified 1 month, 1 week ago by Daryl Dobbs.
    #612007
    Grant Privett
    Participant

    Ah, excellent. I looked and they appear to have a place holder object name in place, so it looks hopeful.

    It could be a lot of fun. It looks like it will be taking a while to get there.

    #612152
    Nick James
    Participant

    It doesn’t look good for us in the UK.

    Assuming that the launch goes ahead at the start of the 2 hour window (12:33 UTC on Monday Aug 29) the geometry for the UK is poor with the spacecraft below the horizon at night for the first week. It is above the horizon in a dark sky on Sept 5/6 when it is at declination -27 and due south around 2100 UTC but, by then, it will be a long way away and close to the Moon in the sky (not a surprise really) low in Sgr.

    It gets to high northern declinations on the way back but by then it is heading for solar conjunction.

    All in all I doubt if anyone will image it from here. A good opportunity to use a remote telescope I think.

    #612156
    Grant Privett
    Participant

    At -27 theres not much hope from home for me then as my dome blocks everything below -10 and a nearby hill blocks everything below -15.

    Damn.

    #612157
    Paul Leyland
    Participant

    Dec is fine from here in LP but whether the sky is clear is another matter. The rainy season is beginning and there is thick cloud tonight.

    #612158
    Nick James
    Participant

    Yes, it’s going to be a challenge. The attached plots show the visibility from my observatory in Chelmsford to give some idea. These show the altitude of the Orion spacecraft, the Sun and the Moon at the date shown along the bottom. On the night of the launch Orion is around 12 deg up at nautical twilight and descending. I don’t know how bright it will be but at 20h on the day of launch it will only be 10 deg up from here and it is already 79000 km away. The ISS at this distance would be around 4th mag and Orion is a lot smaller than the ISS.

    By the time the circumstances get better it is far away and close to the Moon as you can see from the second plot.

    I would love to be proven wrong and would be very impressed if anyone gets this from the UK!

    #612168
    Nick James
    Participant

    Ted Molczan has provided a table of expected magnitudes for the spacecraft (Orion) and the SLS upper stage and spacecraft adaptor (the Interim Cryogenic Propulsion Stage) on seesat:

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

    They indicate that Orion will be 13th mag on the night of launch fading to 17th mag at lunar distances with the ICPS around 1 mag fainter.

    The ICPS will be deflected from the spacecraft trajectory by a disposal burn shortly after trans-lunar injection (TLI). This will target a lunar flyby which will put the stage into a heliocentric orbit. The stage will probably do a propellant dump shortly after the disposal burn as part of its passivation procedure. Sadly we are not going to see that from here but it could be an interesting sight for people in the right place. Have a look at Chris Taylor’s description of the equivalent from the Apollo 8 S-IV-B upper stage:

    https://www.hanwellobservatory.org.uk/news/apollo-8-from-the-other-side-of-the-pond

    JPL Horizons has an ephemeris for Orion but not the ICPS. It is likely that an ICPS ephemeris will appear here:

    https://projectpluto.com/sat_eph.htm

    Good hunting. Please post any images you get on this website.

    • This reply was modified 3 weeks, 6 days ago by Nick James.
    • This reply was modified 3 weeks, 6 days ago by Nick James.
    #612187
    Nick James
    Participant

    An updated ephemeris for the rescheduled Artemis launch time (window opens on Sept 3 at 18:17 UTC) is on JPL Horizons. This has much better visibility for us on the evening of the launch. The spacecraft rises around 20:00 UTC and gets above 40 deg altitude by 21:00. The upper stage separation burn is at T + 2hr 7min so may well be visible from the UK if the sky is clear.

    Let’s hope that they now fully understand the LH2 bleed and the RS-25 cryogenic conditioning problems that scrubbed the last launch and that the weather cooperates on both sides of the Atlantic.

    #612188
    Grant Privett
    Participant

    That sounds very hopeful. Would love to see the burn…

    Of course that means overcast skies plus fog for the next couple of weeks then. 🙂

    #612192
    Nick James
    Participant

    This document has some useful background information on SLS. In particular it has a timeline including the ICPS disposal burn on page 55:

    https://www.nasa.gov/sites/default/files/atoms/files/sls_reference_guide_2022_print_0.pdf

    Nick.

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