Asteroid Zoo Talk

2006RH120 - Is this the Apollo 10 LEM ascent stage (Snoopy)?

  • bonesmccoy2015 by bonesmccoy2015

    Many years ago, the general media began reporting on attempts to identify the exact location of the ascent stage of the Apollo 10 Lunar Excursion Module. The Apollo 10 LEM was named "Snoopy" after the character in the Charles Schultz comic strip "Peanuts". The intrepid Beagle who flew the Sopwith Camel in his WW-1 pilots costume became a decades long symbol of great engineering and piloting for NASA and the next forty years.

    For those unfamiliar with the mission of Apollo 10, the mission was the "dress rehearsal" for the first attempted landing on the moon and featured test flight of the Apollo-era Lunar Excursion Module in lunar orbit.
    Apollo 10 launched from the Kennedy Space Center, Florida on May 18, 1969 and landed on May 26, 1969.

    According to data at USRA, Apollo 10 performed its Trans-Earth Injection burn on May 24, 1969. In reviewing Apollo 10 mission transcripts, the LM Snoopy was jettisoned in lunar orbit prior to the CSM (called Charlie Brown) performing the TEI burn. In doing further research, the crew (Stafford, Cernan, and Young) actually filmed the separation of Snoopy with Charlie Brown using the 16mm film camera. The crew and Mission Control are seen to banter in the mission transcript about Snoopy taking off towards the sun. In Apollo 10 film canister Y, it is possible to see these exact circumstances. The latches appear to be commanded with the air pressure in the closed tunnel adapter section providing sufficient force to separate the two vehicles. Within a few seconds, the LEM disappears in the glare of the sun which is immediately behind the LEM when watching the 16 mm film.

    In reviewing the Apollo 10 Mission Supplemental Report, the Guidance and Navigation team at JSC appear to have published specific solutions sets for the sensor readings and data from Snoopy after separation. It is unclear to me if the vehicle is pressurized or not. If air leaks under pressure from the Ascent Stage, the escaping gases would create a minimal thrust and impart angular momentum on the vehicle.

    From review of some of the mission transcripts, it is clear that JSC (mission control) and the crew of Apollo 10 were attempting to identify where Snoopy moved in relation to the CSM in order to insure that the two spacecraft would not be moving towards each other during TEI. The team at Mission Control appear to have commanded the LEM APS (Ascent Propulsion Stage) to do one burn just after sep and then commanded an APS burn to depletion. The Apollo 10 mission summary supplemental report appears to show the metrics on the velocity and acceleration vectors before, during, and after the APS burn to depletion.

    Apollo 10's lunar module ascent stage is the ONLY remaining Apollo manned flight hardware that is still in space. All other command modules returned to Earth. All other lunar modules either reentered Earth's atmosphere (Apollo 9 and 13) or were either deliberately or eventually impacted on the lunar surface (Apollo 11-12, 14-17).

    Locating Snoopy in Near-Earth space would be a significant scientific accomplishment because (1) the telescope skills required to image, track and identify the object are significant and (2) the computational skills required to appropriately identify orbital elements require extrapolation of much. More interestingly, the development of the SLS system by NASA and the development of the Falcon 9 Heavy booster vehicles could provide sufficient delta-V to permit asteroid rendezvous missions of near-earth objects. If the Apollo 10 ascent module is in a sufficiently close proximity or if other Apollo-era hardware are in a sufficiently close proximity, it would be intriguing to perform mission analysis for potential rendezvous and retrieval of samples from the hardware for ground based analysis and testing.

    In reviewing near-Earth objects, an object called 2006RH120 (aka 6R10DB9) has been previously discussed as a second moon. The object was in an unusual earth orbit in 2006-2008.

    Some information is posted here:

    A Sky & Telescope story is posted here:

    It appears that there was discussion about this object potentially being related to Apollo era hardware. I would appreciate assistance in understanding if there has been publication of the radar data from Goldstone's analysis in 2007. I have been unable to locate an image of the object made from radar data.

    In a paper published in Astronomy and Astrophysics, authors note their photometric observations of the object in 2007 (see: The authors appear to conclude data is suggestive of an asteroid. But intriguingly, they note an effective diameter of 2-7 meters or 3.3 +/- 0.4 meters.

    The Apollo LEM ascent stage was 3.76 meters x 4.29 m x 4.09 meters in size. The size of 2006RH120 concurs with Snoopy's ascent module.

    In JPL's Small-Body Database Browser, the entry for 2006RH120 is at the following URL:;cad=1#cad

    The small-body database listed "close approach data" has an entry listing "1969-May-03 07:42" with time uncertainty of 2 days, 19 hours, and 34 minutes at nominal distance of 0.04302 AU and minimum distance of 0.0081665 AU. Although the minimum distance in the JPL calculation is outside the orbit of the moon (0.0081665 AU is approximately 750,000 miles), the dates put the object in near-earth space within an appropriate time frame to coincide.

    Also, in an Astrogator's Guild posting at, the author performs a masterful exercise in trajectory analysis for Snoopy based upon 3 assumptions (please review his comments if you want more info on those assumptions). In the author's trajectory analysis, I find it intriguing that the object would reappear in the 2000-2008.

    In the Astrogator's analysis, the orbital appears to have a 15 year cycle. In the analysis of 2006RH1120, there appears to be a shorter interval. Though, the wiki-page for this object notes:

    "The next near-Earth encounter is in August 2028 when the object will
    pass Earth at a relatively low speed of 136 metres per second (304
    miles per hour)"

    The question I am raising here for this audience, could 2006-RH 120 actually be the ascent stage of Snoopy from Apollo 10?

    The discrepancy of the dates of closest approach might be related to the delta-V discrepancy from outgassing of materials from the ascent stage following jettison and perhaps propellant leaking gradually inducing a rotational rates on the stage.

    Does anyone know if there are radar images created from the Goldstone observation of this particular object in 2007?

    NHATS has a page analyzing the physics required to visit this object.


  • bonesmccoy2015 by bonesmccoy2015

    Additional comment.
    A key publication in the analysis of 2006RH120 in Astronomy and Astrophysics appears to be at:


  • astrogator_mike by astrogator_mike

    This is excellent. I'll have to see if I can create a trajectory that matches this, and compare it with the others I had on the Astrogators Guild site. I'll post back here when I've got something to look at. Sweet!


  • bonesmccoy2015 by bonesmccoy2015

    Dear Mike,
    I am so impressed with the analysis you publish at the Astrogator's Guild.

    You may already be familiar with the Apollo 10 Mission Summary Supplemental Report written by the MSC GNC Apollo 10 group.

    In reviewing your prior work at Astrogators on Snoopy, the original solution set used to create the lunar escape trajectory is shown in several diagrams.
    I was not clear on the initial solution used in terms of position, orbit, and vectors.
    The problem that I see is that the MSC GNC guys were guessing as to the exact position of Snoopy. When you watch that film and read John Young's comments, he basically says the LM was moving quickly.
    It's hard to say how much delta-Vx was imparted by the air pressure in the tunnel adapter but the force of the air in the tunnel was a fairly strong push.

    By taking a guess at the closed cross-section of the tunnel in meters squared and then guessing on the air pressure in the tunnel, it might be possible to guess the force from air pressure acting on Snoopy and Charlie Brown.

    As a bit of a side note on this topic of Cabin Air Press and psi, note:
    There is a crew transcription where Cernan and Stafford are in Snoopy and Young is in the CM. The crew are attempting to resolve air pressurization issues prior to LEM sep from the CM in lunar orbit. I note that the crew mentions having air pressures of 4.9 psi at one point and 5.4 psi delta-p is mentioned at another point.

    The crew is dealing with issues related to the air pressure not moving lower in the appropriate way. They attempt to throw some of the valves and change flow of air in the tunnel in order to move the clog (presumptively some mylar in the tunnel was interfering with the tunnel depress by moving around and blocking the air flow or valves).

    Although the incident in this part of the mission relates to LEM sep prior to flight, this part of the transcript sheds light on why the crew had air pressure in the tunnel during Snoopy's jettison. The crew were trying various work arounds to complete the cabin depress according to schedule. At the time, the complexity was heightened because there were roll rates imparted to the tunnel and some concerns about the structural limits in the tunnel; and the crew was out of communications range (LOS) at the time. The data may have some bearing on the situation later in the mission when Snoopy is jettisoned.

    I'm having trouble figuring out the actual air pressure in the tunnel but given the humor and personality of the crew members, I would not be surprised if the crew had several psi in the tunnel. If that tunnel is about 1 meter in diameter, the surface area of the tunnel might be pi * (0.5 m) squared. Totally guessing, but it looks like the cross sectional area of the tunnel would be about 0.75 meters squared.

    Assuming cis-lunar space is fairly close to a total vacuum, you'd be exerting 5 psi against 0.75 meters squared area. Via a look-up table, it appears that 5 psi is about 35 kiloPascals. By unit conversion (kPa = 1000 Newtons/square meter), the air pressure against the hatch might have been around 35,000 Newtons/square meter.

    According to this reference table:

    The mass of the Apollo-10 LEM at jettison was estimated at 7663 lbs. This is roughly 3500 kg.

    The force of the air is acting on the cross section of the hatch. Therefore, 35,000 Pa x 0.75 square meters) = 26250 Newtons

    Since acceleration = force/mass = 26250 Newtons / 3500 kg = 7.5 meters/sec/sec

    That number looks about right when you look at Reel Y. The rate stops fairly quickly but the force is imparted on both spacecraft over several frames of the film. The 16 mm camera appears to be shooting the images at about 25 frames per second. Therefore, I think it's reasonable to conclude that the force of the air is lasting about 0.2 second (or about 5 frames). After locating a digital copy of Reel Y on a NASA site, I clipped the film for the Snoopy jettison sequence and then applied a time counter which includes a frame-by-frame count. At 2 minutes 2 seconds / frame 17 into the downloaded version of the Reel Y, I see a deflection in the LEM metal skin around the docking window. That deflection appears at frame 17 and appears to last until frame 23. From this deflection of the mylar I'm guessing that the air pressure took 0.2 seconds to escape the tunnel.

    If acceleration of 7 m/s/s would be imparted across 0.2 s, I'm guessing about a 1 meter / sec rate. When you look at the film, that's about what it looks like. So, the numbers appear to converge with a 1 to 2 m/s Delta Vx motion.

    I was attempting to evaluate this "Delta-V" because of the possibility that the Delta-V might not be accounted for in MSC-00126. The authors of NASA Report MSC-00126 Supplement 2 give several different illustrations and graphs on the AGS rates. These are detailed graphs and rates, including velocities off the AGS.


    Note the discussion regarding the APS burn to depletion on pages 6-3 to 6-5

    However, in my amateur look at the report, I could not identify if the delta-V from LEM sep was described. Imparting another 1 - 2 meters per second would not be very important for the APS test that MSC performed. In fact, the rates involved are not relevant to measure for the APS Burn to Depletion tests. The interesting thing is that when you look at the illustrations for the APS Burn to Depletion, it does not appear that the prior APS burn or the LM Sep deltas are included in the figures.

    For those who are reading along, the Apollo 10 APS Burn to Depletion test was meant to evaluate the accuracy and alignment between the sensors and the rates in cis-lunar space. The sensors and guidance computers appeared to perform well. In reviewing the APS Burn to Depletion charts, it is difficult for me to read the GETs (ground elapsed time figures) on the axis of some of the charts. It is hoped that some of the NASA vets might be able to review those notes in order to correlate the LEM Sep delta V in the rates and sensor readings.

    Although a 1-2 meter per second difference may be inconsequential for the APS Burn to Depletion data, this difference could create a significant change to the lunar escape trajectory solutions set.

    Mike's prior analysis correctly predicted the orientation of the Snoopy to the sun. When you look at the actual film from Apollo 10, the sun is in a matching orientation. This also suggests that the delta V is towards the sun. This delta-V is intriguing because it causes me to wonder if that delta-V may be related to the 2 week difference in the JPL NEO database (suggesting closest approach around May 8-10, 1969) and the actual lunar escape date of May 24, 1969, (two weeks later). The exact orientation, heading, and vector in inertial space can be identified from the MSC report cited above because the velocities at the end of the APS Burn to Depletion maneuver were reported. The only question is exactly where was the LEM at the time of the APS Burn to Depletion manuever.

    Note that there are TWO burns of the APS following jettison. I was attempting to locate specific data on any LM RCS thruster commands and the exact solution set on the two APS burns following Snoopy's jettison but I was not able to locate those specific data. Hopefully, someone from the MSC team might know where that dataset is specifically recorded either in MSC-00126 or another location.

    The Astrogators website is a wealth of info to any person learning orbital mechanics.

    While there are many NEOs in the JPL database, I'm skeptical that there are many NEO's in the JPL database which (1) have a fly-by with Earth in May 1969, (2) which are 3 meters in size, and (3) have an orbital trajectory which appears to loosely correlate to Mike's hypothetical trajectories based upon the models in Astrogator.

    It would be really great if someone assembled the Goldstone radar data during the 2007 pass. I am also still looking for that dataset.

    Best wishes Mike and Nick - you have a great collaboration and I hope that my analysis has contributed to the discussion. If this object is not Snoopy, it sure is acting like a Snoopy follower. If it's not Snoopy, then might I recommend the asteroid be called Woodstock?

    Stay in touch! If you speak with Commander Cernan about this hunt again, please pass him my best regards.

    As John Young said during the Pre-STS-1 press conference... "Spaceflight is an old man's business." 😃


  • bonesmccoy2015 by bonesmccoy2015

    Just found an interesting document for any interested in the Apollo 10 Snoopy hunt.
    Apollo 10 ATG Transcript at

    Page 528 gives some clues on gimbal angles for the CMP and therefore the LMP at jettison.
    Mike may find this helpful in the lunar escape trajectory model for Snoopy.
    Also, you can see the exact timing of the sep.

    04 12 21 30
    CC: Charlie Brown, this is Houston. Your gimbal angles for attitude after SEP are roll 180, pitch 252, and yaw three balls.
    LMP: Roger, Roll 180, pitch 252, and yaw is all balls.
    CC: That's affirmative

    04 12 21 01
    CMP : And when do you want us to separate, Joe?

    04 12 21 09
    CC: OK. Want - We can go ahead and separate now, Charlie Brown

    04 12 22 19
    CMP: Okay

    04 12 24 15
    CDR: Okay Houston, We'll give you a countdown. We're all set to go for SEP. Right?

    04 12 24 19
    CC: That's affirmative, Charlie Brown. We're standing by for your count.

    04 12 24 29
    CDR: Okay. Give you a five count. 4, 3, 2, 1...

    04 12 24 37
    CDR: FIRE.

    04 12 24 42
    CDR: Cabin pressure is holding. Snoop went some place.

    04 12 26 17

    CMP: Houston, Charlie Brown, Over.

    CC: Roger, Charlie Brown. GO,

    CMP: Man, when he leaves, he leaves.

    CC: yes, OK. Don't back into that dude, now John, when you get turned around. Are you keeping it in sight?

    CDR: Yes, OK. Joe, he took off so fast, he's gone; he went right into the Sun.

    CC: Roger. Copy.

    CDR: We don't have any idea where he went. He just went boom and disappeared right into the Sun.

    CMP: If you give us gimbal angles and allow us to burn out of here, we'll be okay.

    CC: OK Stand by.

    04 12 28 50

    CDR: Hello, Houston. Charlie Brown.

    CC: Roger, Charlie Brown. Go ahead

    CDR: OK. Look, let's take a quick look at these orbital mechanics. When we separated ORB rate, he was straight up, and he had that 5 psi on the tunnel; and he took off like scaled rock, straight up. OK?

    CC: Roger that.

    On page 534 - you can see the timing on Snoopy's APS ignition (not sure if its the first or second APS ignition).

    04 12 52 15

    CC: OK, we got ignition on Snoopy, Charlie Brown.

    LMP: Hey I may see it out there; I'm not sure but I think I do. I do!

    CC: Very good.

    LMP: I'll see if I can tell you when he burns out. That's a long burn, though, isn't it? 4 minutes.

    CC: Yes. Can you tell which way he's going?

    LMP: Dave, it's just fire to me; I think he's going up, but see, I'm not rightsideup either, but-

    LMP: He's going, Joe. As long as I can see the fire, I guess he's going the other way.

    CC: Roger. From down here he looks like he's doing real good, Gene-O.

    LMP: Hey Joe, would he be burning away from us, sort of like maybe his attitude is local horizontal or close to it?

    (page 535)

    04 12 54 32
    CC: Charlie Brown, this is Houston. That's affirmative. He should be going in that direction.

    04 12 54 38
    LMP: Yes, I got him out my right-hand window here; he's getting smaller, and he's still on fire. How much more burn time has he got?

    04 12 54 44
    CC: Stand by, I'll find out.

    (note; The LMP and Capcom trade banter about setting in the LM and discuss what was left in the LM)

    LMP Man, we had PLSS's and probes and drogues and all sorts of things on there. How far will you be able to track him?

    CC: Probably for several hours

    LMP Is he really going to the Sun?

    CC: Well, he's going in that general direction.

    LMP: God, I feel sort of bad about that, because he's a pretty nice guy (not sure if the word is guy or dog - illegible text in the transcript), he treated us pretty well today.

    It turns out that NASA MSC did know the rates from the LM jettison.
    Page 543
    at 04 14 31 24
    Capcom : 10, just for your info, we show about 9.7 foot a second separation, and we think it was just from that cabin venting on Snoopy after you'd separated.

    at 04 14 32 15
    CDR: Houston, 10. Did you say that Snoopy's cabin pressure went down to zero? Over.

    CC: That's affirmative, Tom. It went all the way down. Down to zero in 10 seconds, Tom.

    LMP: Hey, Joe, I went back in there a second time to make sure that dump valve was in AUTO, so it - something must have happened, because it was in AUTO.

    At page 554 Capcom gives the crew some other news on Snoopy's tracking during their sleep period.
    04 20 37 29
    'Apollo 10, this is Houston. You got up kind of early this morning. We were going to let you sleep in for quite a while yet. We've got a little information that will be of interest to you. Your consumables ere away ahead of schedule as usual. We have you in a 65.9 by 55.6 orbit. Your spacecraft looks real good. You might be interested to know that the LM ascent stage is 23 000 mi]es from the Moon heading straight up at 5400 feet per second, and haven't quite beenable to tell yet whether it's going into orbit around the Sun or if it's going to head straight at the Sun.

    later in the page
    CC: We're still tracking him.
    LMP: You can?

    Page 555
    CC: That's affirmative. We're still tracking him and checking the LGC, and so forth.
    CC: Matter of fact, we just got an E-MEMORY dump of him. Oh...
    LMP: You got an E-MEMORY dump?
    CC: That's affirmative, Old Snoop, he doesn't give up.


  • bonesmccoy2015 by bonesmccoy2015

    Very interesting to find the NEODys dataset giving a closest approach of June 2, 1969, and a minimum distance that is offset from JPL's calculation.

    JPL gave May 3, 1969.

    NEODys data set gives:
    Planet Date MJD Nominal
    (au) Min possible
    (au) Stretching
    (au) Width
    (au) Close app

    It appears that the two models (JPL NEO ephemeris and NEODyS) could form two bounds on the estimate. The difference is intriguing because it suggests that different perturbations or influences on the trajectory may be accounted for or not.

    For instance, does the moon's gravitational influence or other planetary bodies (Jupiter and planetary conjunctions for instance) part of the models?


  • astrogator_mike by astrogator_mike

    I've sent Chuck Deiterich this link, perhaps he'll comment. The thing I concluded from my previous look at this was that we simply weren't going to get accurate enough information to be able to tell where the spacecraft was. DSN didn't do any real tracking of Snoopy after it left (as far as I can tell) so all we have to go on are estimate state vectors and estimated delta-v numbers. The "burn to depletion" maneuver is meant to be sloppy (in terms of delta-v) so even if we could nail down the air pressure force, etc. very accurately, we'd still have a lot of slop in the escape delta-v. This slop shows up as a huge error 15 years later the next time the spacecraft gets close to the Earth, and gives you a massive spread of possible trajectories after that next flyby. I think the best we're going to be able to do, is to show that an object with a known trajectory (such as the one you're suggesting here) could possibly be Snoopy. If we can show that a trajectory leaving when Snoopy did, within the errors of the information we have, could possibly be this object, then I think we'll have something. We should see if we can get Paul Chodas to look at this. I emailed back and forth with him in 2002 about the Apollo 12 stage finding. They've looked at these sorts of things before.


  • bonesmccoy2015 by bonesmccoy2015

    The massive spread of possible trajectories is understandable.
    Snoopy's vectors have a certain error or accuracy at the time of the burn.

    I've wondered how NASA could track with accuracy the orbital parameters of Charlie Brown and Snoopy.

    I'm guessing that the IMUs on both spacecraft had a sensor drift which would have been rather difficult to ascertain with specific accuracy during Apollo 10 because it was the first time the two spacecraft were flown around the moon. In reading about Snoopy's final mission goals, it appears that the APS Burn to Depletion was a maneuver to test out the sensor and system performance in cis-lunar space. Since the sensor and system performance was not fully defined prior to the burn, it is understandable that there could be larger uncertainties in the dataset during 10.


  • bonesmccoy2015 by bonesmccoy2015

    In continuing the analysis of 2006RH120 - several interesting analyses came to light tonight.
    First, let me post the interesting work on two different web pages.
    The comments of the author trace the history of observations on this object. The author writes about Bill Gray's analysis in the 2007 timeframe.
    "On his 6R10DB9 page he comments that calculations to determine the area to mass ratio for solar radiation pressure calculations lead to an uncertainty of only about 5% in its value and adds "the area/mass ratio is way too low to be a rocket booster".

    Bill Gray's analysis could be correct. It may not be a "rocket booster". Although Bill Grey's 6R10DB9 analysis page is now off-line, I was able to find a 2012 copy of his page on

    Here's his comments on B44E

    Here's his page on 2006RH120

    I have copied and pasted Bill Gray's original comments with some highlights that I've done in bold-italic.

    I'd assumed this was a rocket booster, but the 12 December 2006 observations from (G96) Mt. Lemmon made this harder to believe. They allowed the area/mass ratio to be computed to within about 50%. The March 2007 data from (A60), (G96), and (J95) have narrowed that down to about 5%, and the area/mass ratio is way too low to be a rocket booster. If the object is two or three meters across, it would have a mass of a few tons, about what a low-density rock might have. I hate to say this, because it seems so implausible... but this looks a heck of a lot like a natural object.
    Peter Birtwhistle got four more observations of this object on 15 June and more on 18/19 June which have a substantial effect on the orbit. In particular, the area/mass ratio has increased from 0.00082 m2/kg to .0011. Further data from G96 confirms this. In truth, utter stability in the AMR would be a bit surprising, since it would indicate a spherical object. If it's at all potato-shaped, the AMR would be greatest when the spin axis was pointed closest to the sun, and would show considerable variation. It could be that the radar data will support that idea.
    The variations in area/mass also make it harder to fit the orbit, and the root-mean-square error has climbed quite a bit with the latest observations included. We've seen similar effects with various artificial objects such as J002E3, the Apollo rocket stage found a few years ago.

    Continuing with my analysis:
    Data are reported by NASA at

    Here are some mass characteristics for Snoopy's Ascent Stage.

    Note that the mass of the A10 Ascent Stage is considerably heavier than other LEMs.
    A10's ascent stage has a weight of 7663 lbs at post-docking jettison.
    The other Apollo LEM's have a listed weight of around 5800 lbs at post-docking jettison.

    To give the observer an idea of what the cross-sectional area of the LEM appears to be, one can compare to photos of the Ascent Stage of the LEM in flight.

    I have discovered a good LEM report at: Historic folder/lm.pdf

    This particular report includes great photos of the ascent stages in production.

    It also includes a data table which lists data on the LEM Ascent Stage for Apollo 10.

    Diameter: 14.083 feet

    Height 12.333 feet

    Crew compartment ht - 7.667 feet, depth 3.5 ft.

    Dry weight 4,791

    Let me walk through a barebones area/mass ratio for Snoopy.

    Snoopy's mass is stated by NASA at 7663 lbs, or 3,476 kg.

    A diameter of 14.1 feet = 4.298 meters - say 4.3 for convenience. Then, radius = 2.15 meters

    Area of circular object is pi x radius squared

    3.14 * (2.15 meters) squared = 14.5

    Therefore, I get an area of 14.5 meters square.

    Converting the dry weight (recall that the A10 LM APS burn was to depletion) and adding some weight for the PLSSs and gear Cernan stated he put in the LEM, say dry weight = 4791 with 200 lbs of other material

    Therefore, guessing 4800 lbs = 2177 kg

    Area/kg = 14.5 m2 / 2177 kg = 0.0067 m2/kg

    Note that this number is estimating based upon a totally reflective cross-section, which is highly unlikely given the angulated surface of the LEM ascent stage.

    Taking Bill Gray's reported 0.0011 ratio.

    0.0011 m2/kg x 2177 kg = 2.4 meters square area would need to be obtained.

    If this object is the Snoopy Ascent stage, this number implies it would have to be returning only 16.5% of the radar energy and reflecting nearly 84%.

    I suppose here, the question is now whether or not a cross section of the LEM would reflect that much energy. Perhaps, that might be experimentally tested against the remaining LEM ascent stages on museum display.

    Bill Gray's note that "it would have a mass of a few tons" is particularly intriguing. He may be correct. If it's snoopy, then the mass is reportedly 2 metric tons. He's correct on the mass. The only issue missing here is the reflectivity of the LEM to radar signal.

    In my amateur eyes, the LM looks angulated and would probably not reflect very much radar signature unless the APS was directly aimed at the Earth...which seems improbable.


  • bonesmccoy2015 by bonesmccoy2015

    The other way to double check our assumptions here is to use the reported 0.0011 m2/kg number against a the same cross sectional area of 14.5 m2

    14.5 meters squared / 0.0011 = 13,181 kg
    This number is probably the reason people concluded that this was not a booster.

    Furthermore, if the object is only 3 meters in diameter, then the radius may be approximated at 1.5 m and an area of say 7 meters squared.
    This would give you a mass of about 6350 kg, three times more massive than the dry weight of the LEM ascent stage.

    I think this is probably the reason that the astronomical community discounts this object as the Apollo 10 LM.


  • bonesmccoy2015 by bonesmccoy2015

    If Nick talks with Gene Cernan, I would like to list some questions in no particular order:

    What were the objects placed in Snoopy prior to jettison?
    In the A10 ATG transcript Gene mentions to Joe Kerwin that the PLSS and Drogue were put in there... can we get some more detail on the list of things put in Snoopy in order to estimate mass? Can Gene estimate the mass of the objects? He knows how many pounds the PLSS was. He might be able to guess on the weight of the other stuff too.

    NASA gives a mass estimate for Snoopy that is much higher than for A17's Challenger.
    I'm guessing that this is related to fuel quantity aboard the LM at jettison. What does Gene think about the mass estimate on Snoopy in the Apollo Mission summary data? Does he think that sounds right? A 2000 lb difference is a big deal in spaceflight.

    It would be of interest to know if he recalls watching Snoopy's APS burn. Does he recall where the CM was? Was it on a track over a particular set of craters and was he watching the LM move below the CM as he was looking down on the LM APS burn? The Apollo ATG transcript gives me the impression that he's seeing Snoopy ignite his engine and then Snoopy burns his engine right through the terminator and into the lunar dark side.

    For someone observing the ATG transcript, it's unclear how Charlie Brown and Snoopy aligned their platforms. Does the platform alignment in lunar orbit get oriented in the IMU to a specific plane in order to generate the gimbals? I see in the ATG transcript where John Young is communicating with Capcom on the gimbals at Snoopy's jettison. But, I can not locate a reference document that describes the reference frame for the gimbals. I'm wondering if they used the plane of lunar equator, the ecliptic plane, or some other inertial reference.


  • thrashc by thrashc

    Bill Gray's website has moved: is most current.

    If you go back to the photometric analysis of 2006 RH120 in Kwiatkowski et al. (2009), linked above, it's fairly clear that this object doesn't show the optical signal that Snoopy should.

    First, it is oblong, with an elongation ratio greater than 1.4. The Lunar Module ascent stage is much more compact: given the dimensions quoted above, the maximum elongation ratio is ~4.29/3.76 = 1.14.

    Second, it is faint, with an absolute magnitude of 29.9 +/- 0.3. The 3.3 m diameter is calculated based on an assumed (i.e., asteroidal) albedo of 0.18. Say that the Ascent stage surface is a 50-50 mix of aluminium sheet (albedo ~0.85) and black paint (albedo ~0.08). Then the unresolved total albedo should be ~0.46. Inverting the Fowler and Chillemi (1992) formula used in Kwiatkowski et al. (2009), the ascent stage should have an absolute magnitude of ~28.0 -- far too bright to be the same object.

    Between this and Bill Gray's analysis of area-to-mass ratio, it seems unlikely that 2006 RH120 is the Apollo 10 ascent stage, despite the similarities in the orbits.


  • bonesmccoy2015 by bonesmccoy2015

    thrashc makes a good point regarding the elongation ratio though I am not as clear regarding this specific data point.

    A good description of the LM is located here:
    Note page 10 - a schematic of the cross-section of the LM ascent stage drawn from the top-down perspective.

    The appearance of the LEM ascent stage on a radar study would vary with the face of the LM aimed at Earth.
    Note the following photos of LM AS in Apollo ops.

    These images show that the potential radar return will vary with the face of the LM AS that is facing the Earth.
    The LM AS will create a significant variance in the radar data depending upon the orientation of the module to the incident radar signal.
    And, the variance in the materials on that surface would suggest that very specific data analysis would need to correlate the radar analysis with the rotation rate of the object and the materials on that side of the module.
    It does not appear that this type of analysis has been previously undertaken. It would be of interest to draw up a table with the predominate color and appearance of that face of the LM AS based upon A10 film footage.
    I may create a digital film and post to Youtube for reference.


  • cffd by cffd

    I only worked the launch phase of Apollo 10, but I was in the Control Center when the CSM separated from the ascent stage. (Retros always worried about recontact.) During one of the pre-mission planning meetings, the flight dynamics team recommended that the crew execute a specific maneuver sequence to assure no recontact of the two vehicles. But the crew felt they could just separate from it and get out of the way.

    The tunnel between the LM ascent stage and the Command Module was not depressurized, and when they fired the bolts to separate, the air pushed the ascent stage away right into the Sun. They couldn’t even see it, so the crew didn’t do anything, and a bit later, the LM did a burn and went into solar orbit. On Apollo 13, I remembered what happened during the Apollo 10 Ascent stage separation and recommended it for CM LM separation prior to entry, which worked very well.


  • bonesmccoy2015 by bonesmccoy2015

    To cffd -
    2 questions for you -

    a) What is the reference frame for the gimbal angles discussed between capcom and John Young (CMP)?
    There are gimbal angles sent up to John prior to the LM being jettisoned. Those angles determine the pointing of Charlie Brown and by extension the movement of Snoopy at LM sep.

    b) Is there a list of LM RCS and APS thruster commands recorded somewhere with the time of the firing? Such a list would provide the orientation and timing of the LM during the APS burns. On the prior page to this one, it appears that there were two APS burns after jettison. In the A10 ATG transcript, there is also banter between Cernan (LMP) and Capcom regarding visual on Snoopy during the APS Burn to Depletion maneuver.

    -- by the way, great work on A13 - You must have been working at the time Glenn Lunney was Flight Director during 13, if you were on his team. I had a chance to meet Lunney many years ago as I did an interview for a local newspaper. Lunney said of the work he did at MSC, he was probably most proud of the work during Apollo 13. I think most close observers of manned spaceflight would agree.


  • bonesmccoy2015 by bonesmccoy2015

    Two references to Apollo 10 Snoopy maneuvers and data.


    Once docked, the LM crew transferred the exposed film packets to the CM. The LM ascent stage was jettisoned at 108:24:36. A 6.5-second separation maneuver at 108:43:23.3 raised the LM orbit to 64.0 by 56.3 n mi. This was followed at 108:52:05.5 (about one revolution after jettison) by a 249.0-second remote control firing to depletion of the ascent engine. This burn, commanded as planned, utilized the LM ascent engine arming assembly and was targeted to place the LM into a solar orbit. Communications were maintained until LM ascent stage battery depletion at about 120:00. The ascent stage batteries lasted about 12 hours after LM jettison.


    LM Ascent Stage Propellant Status
    Apollo 10
    Fuel 981 lbs, Oxidizer 1650 lbs, Total 2631 lbs.

    Consumed by RCS
    Fuel 13.9, Oxidizer 28.0, Total 41.9 lbs.

    Consumed by APS Prior to Jettison
    Fuel 67, Oxidizer 108, Total 175

    Total Consumed
    Fuel 887, Oxidizer 1408, Total 2295

    Not sure if this data helps for Mike and any attempting to calculate S-IV B trajectories...

    A10 S-IV B data (as compiled by the author from Saturn V launch vehicle flight evaluation reports) as follows:
    GET 078:51:03.6
    KSC Date May 21, 1969
    GMT Date May 21, 1969
    KSC Time: 07:40 PM EDT
    GMT Time: 23:40 hrs

    Lunar Radius of closest approach 2,619 (n mi)
    Altitude above lunar surface 682 (n mi)
    Velocity increase due to lunar gravity (n mi/sec) 0.459

    S-IV B Solar Orbit Conditions
    Semi-Major Axis (n mi) 77,740,000
    Eccentricity 0.07256
    Aphelion (n mi) 80,280,052
    Perihelion (n mi) 69,417,732
    inclination (deg) 23.46
    Period 342 days

    Side note: This particular document notes that the S-IVB for Apollo 8, 9, 10, and 11 are all in heliocentric orbits. I'm now wondering if the object known as B44E is one of these objects.


  • thrashc by thrashc

    Highly doubtful. 6Q0B44E has an absolute magnitude of 30.1. This implies a size in the ~3 m range. A Delta II second stage (e.g., from GRAIL, object 2011-046C) has a signature of this level. J002E3, the Apollo 12 S-IVB rocket body, has an absolute magnitude of 26.4 -- more than 30 times brighter.


  • cffd by cffd in response to bonesmccoy2015's comment.

    Bones: Glynn (note spelling) hired me and I worked many shifts with him starting with AS201, the first Apollo flight. A very close friend.
    I need to think about the other questions.


  • bonesmccoy2015 by bonesmccoy2015 in response to cffd's comment.

    Glynn (note spelling)
    Thanks for the correction. At midnight when I was writing that post, I knew I had an error in there some where. 😃

    Glad that Nick is continuing to build information flow about NEOs and NEAs.

    Identification of these objects certainly seems to push the limits of current technology and science. And, without the NASA reports being published, it would be much more difficult to learn about how the nation went to the moon.


  • cffd by cffd in response to bonesmccoy2015's comment.

    Bones: You may already know the following about the gimbal angles. The Apollo IMU had three gimbals (the Gemini had 4 gimbals) and if the middle gimbal angle ever got to 90 deg the platform would lock and tumble (red zone on 8 ball). The crew’s 8 ball or attitude indicator read the exact gimbal angles from the IMU. (The shuttle had transformation matrices between the platforms and 8 ball). The ground would compute a matrix (called REFSMMAT) to give the crew an easy 8 ball to read for example R=180, P=0, and Y=0. So probably for the LM jett, a REFSMMAT was computed to make the 8 ball easy to read and put the LM in the correct attitude for the APS burn. The REFSMMAT defined the IMU alignment with respect to earth centered inertial for mean of 1950. I hope I remembered this correctly.

    According to the NASA HQ post flight report, there was only one APS burn after LM jettison. See excerpt below:

    ”Once docked .to the CSM, the two LM crewmen transferred with the exposed film packets and the LM Hasselblad camera to the CSM. The LM Maurer sequence camera and primary lithium hydroxide canister (both of which incurred inflight problems) were also transferred in order that these items could be inspected post flight. The CSM was separated from the LM at 108:43:30 GET using the SM RCS. About one revolution after docking, the LM APS burn to depletion was commanded by the Manned Space Flight Network (MSFN), as planned, utilizing the LM Ascent Engine Arming Assembly, 108:51:01 GET for 213 sec and delta V 3838 fps. This burn was targeted to place the LM in a solar orbit, LM/MSFN communications were maintained until LM ascent stage battery depletion at about 120 hours GET. The ascent batteries lasted about 12 hours after LM jettison,”