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During the Apollo program, we launched a total of 9 Lunar Modules (LM's). The Ascent module from Apollo 10, or "Snoopy," is unique in that it was neither deliberately crashed into the Moon (Apollo 11, 12, 14-17) or the Earth (Apollo 9 and 13). It was instead sent into a heliocentric orbit as part of a burn-to-exhaustion test and NASA stopped tracking it shortly thereafter in 1969.

I know that a group of students and amateur astronomers set out looking for it in 2011, and in 2015 there was some speculation that snoopy was WT 1190F which ultimately re-entered the earth and burned up; but I can't seem to find if anything was verified from either effort/speculation.

What ultimately became of the 2011 efforts to find Snoopy? Where would one start if one were attempting to find it? Why is the search area so large if the starting conditions are known?

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What ultimately became of the 2011 efforts to find Snoopy?

It was left in the hands of the Faulkes Telescope Project:

"Imagers with Registered Faulkes telescope accounts will be able to get the latest coordinate data on areas we'd like searching on this web-page. If you do wish to use any of your allocated telescope time on this project, please adopt the following naming style for your observations.

SNOOPYYYMMDDTTTT

Eg: SNOOP1108231400 - would be 2011, 23rd of the 8th at 14:00UT. This will make data searches for our team and for anyone who wishes to assist in the hunt much easier.".

Apollo 10: Where's Snoopy?

Where would one start if one were attempting to find it?

The Smithsonian National Air and Space Museum gives it's location as:

"Apollo 10 'Snoopy' (LM-4) - In heliocentric orbit".

See this space.SE question: "Where were the various Apollo Lunar Modules (LMs) discarded?"

Why is the search area so large if the starting conditions are known?

Looking for a known object, WT1190F, at a specific location is expensive and difficult, see:

"The observing campaign on the deep-space debris WT1190F as a test case for short-warning NEO impacts" (Oct 20 2017), by Marco Micheli, Alberto Buzzoni, Detlef Koschny, Gerhard Drolshagen, Ettore Perozzi, Olivier Hainaut, Stijn Lemmens, Giuseppe Altavilla, Italo Foppiani, Jaime Nomen, Noelia Sánchez-Ortiz, Wladimiro Marinello, Gianpaolo Pizzetti, Andrea Soffiantini, Siwei Fan, and Carolin Frueh, on page 4 they explain:

"Discussion

The observations obtained in this campaign prove that, to achieve complete observational coverage of an incoming object on short notice, it is necessary to develop a network of instruments of different classes, each of which is capable of providing a given type observation covering a specific niche in the overall observational strategy.

In particular, it is often necessary to have access to:

  • At least one large telescope (e.g. VLT), which allows for cutting-edge observations (such as spectroscopy at very faint magnitude levels) early in the approach phase. At the same time, being an expensive resource, a telescope of this class can only be obtained on short notice for a limited amount of time.

  • One or two mid-class telescopes (e.g. Loiano), which can be used with much more flexibility, for multiple nights, but may not be sensitive enough at large distances.

  • A network of small telescopes (e.g. Lumezzane), which can be triggered even on very short notice and made available for extended period of time, and are ideal to cover the last phases of the impact trajectory from multiple locations.

If you know where to look this is what you would see, can you spot the object?

WT1190F

Figure 1: An illustrative astrometric image, taken along the night of 2015 November 12, just a few hours before the WT1190F atmosphere entry, with the 1.52 m “Cassini” telescope of the Loiano Observatory (Italy). The telescope was tracking non-sidereally at the apparent angular motion of the target (which appears as a point source near the center of the field), therefore all astrometric reference stars in the frame are severely trailed (approximately 10 in this example). A correct astrometric reduction of a frame like this requires to fit every reference star with a trailed model, to properly determine their centroid.

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JPL Horizons has some trajectory information for Snoopy, but it cannot be used to determine where Snoopy is today. However, it may be of interest to see what Snoopy's orbit originally looked like.

From the Snoopy body data file:

Launched: May 18, 1969 @ 16:49 GMT/UTC from Kennedy Space Center, USA

The Lunar Module (LM), whose later ascent-stage post-jettison trajectory is represented here, came within 14.4 km of the lunar surface (May 22 @ 21:30:43 GMT/UTC), the point where the powered descent to the lunar surface would have begun for an actual landing.

During autonomous lunar orbit operations, and after closest approach, the LM then jettisoned its descent stage at a selenocentric altitude of 58.2 km. Because the crewed LM ascent stage was not launched from the Moon's surface, docking with the Command Service Module (CSM) in lunar orbit was achieved with considerable propellant remaining on the LM. After docking and crew transfer from the LM to CSM, the LM was jettisoned and the surplus propellant expended in ground-commanded separation and depletion burns, ultimately departing the Earth-Moon space with a heliocentric trajectory estimated here.

SPACECRAFT TRAJECTORY: The trajectory here is a reconstruction of the Apollo 10 Lunar Module ascent stage ("Snoopy") departure trajectory developed by Daniel R. Adamo under contract to NASA in 2012. The trajectory spans the time interval from 1969-May-23 05:38 to May 28 @ 00:06 (GMT/UTC).

To extrapolate to future times, the following heliocentric IAU76 J2000 ecliptic osculating elements can be manually input into Horizons as starting conditions for a ballistic numerical integration using the telnet or e-mail interfaces:

EPOCH= 2440369.50 ! A.D. 1969-May-28 00:00:00.0 (TDB)
EC= 1.019060921246732E-01
QR= 8.529502470438327E-01
IN= 1.768522392707621E-01
OM= 6.388513395075357E+01
W = 4.378387492993282E+01
Tp=  2440246.670238981955

... where

EPOCH    Epoch Julian Day Number, Barycentric Dynamical Time
  EC     Eccentricity, e
  QR     Periapsis distance, q (au)
  IN     Inclination w.r.t xy-plane, i (degrees)
  OM     Longitude of Ascending Node, OMEGA, (degrees)
  W      Argument of Perifocus, w (degrees)
  Tp     Time of periapsis (Julian Day Number) 

Uncertainties and errors in the extrapolated position prediction will increase as the time from the EPOCH increases. Predictions for this man-made object years past the EPOCH are problematic due to unmodeled-but-cumulative solar pressure and out-gassing accelerations, yet no further tracking data to characterize the forces.

The Sidereal orbit period is 338.06588 days, and the semi-major axis is 0.9497339 AU.

As mentioned, we can feed those orbit elements to Horizons to get trajectory data. The results should be reasonably accurate for the first year or so after the epoch, but they will certainly not be correct for the present era.

FWIW, here's a Horizons query for Snoopy that covers the timespan given above.

Here's a heliocentric plot of Snoopy (red), the Earth (blue), and Venus (green) from 1969-May-24 to 1970-May-24, using a time step of 7 days. The numbers on the orbits are plotted every 4 weeks. The horizontal line from the Sun is the equinox line. We're looking down onto the ecliptic plane, from the north. Snoopy's orbit is (was) only very slightly inclined from the ecliptic plane.

Earth, Venus & Snoopy

That plot was created using a version of my 3D orbit plotting script, originally posted on Astronomy.SE. Here's the modified version, which contains the orbital elements for Snoopy. To specify the Snoopy elements as a target, use a semicolon ;. Please see the Astronomy.SE post for further info on using the script.

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