Talk:Clementine (spacecraft)

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Did they see the Apollos' remains with the hi-res camera?

  • Actualy, even with Clementines hi-resolution camera, it still couldn't see objects the size of the lunar landers. Just for the record, the Moon Landings weren't faked. :) The QBasicJedi 17:32, 24 June 2006 (UTC)

Mission Section Lifted[edit]

"The mission had two phases. After two Earth flybys, lunar insertion was achieved approximately one month after launch. Lunar mapping took place over approximately two months, in two parts. The first part consisted of a five hour elliptical polar orbit with a periapsis of about 400 km at 30 degrees south latitude and an apoapsis of 8300 km. Each orbit consisted of an 80 minute lunar mapping phase near periapsis and 139 minutes of downlink at apoapsis. After one month of mapping the orbit was rotated to a periapsis at 30 degrees north latitude, where it remained for one more month. This allowed global imaging and altimetry coverage from 60° south to 60° north, over a total of 300 orbits. After an Earth to moon transfer and two more Earth flybys, the spacecraft was to head for Geographos, arriving three months later for a flyby, with a nominal approach closer than 100 km. Unfortunately, on May 7, 1994, after the first Earth transfer orbit, a malfunction aboard the craft caused one of the attitude control thrusters to fire for 11 minutes, using up its fuel supply and causing Clementine to spin at 80 rpm. Under these conditions, the asteroid flyby could not yield useful results, so the spacecraft was put into a geocentric orbit passing through the Van Allen radiation belts to test the various components on board. The mission ended in June 1994 when the power level onboard dropped to a point where the telemetry from the spacecraft was no longer intelligible."

The above passage is directly identical to a passage on the NASA website Should this passage be deleted and rewritten?

Jmhaskins (talk) 19:53, 30 September 2009 (UTC)jmhaskins

"Lost and Gone forever"[edit]

"The project was named Clementine after the song "Oh my Darlin' Clementine" as the spacecraft would be "lost and gone forever" following it's mission."

I always thought that they named it Clementine because that song was a mining song from the Gold Rush days, and similiarly, Clementine would be "prospecting" for things on the Moon. I can't remember where I heard this, though.The QBasicJedi 17:16, 24 June 2006 (UTC)

After reading the article, I can't help but wonder: where is the Clementine spacecraft now? Is it still in geocentric orbit as space junk? It didn't disappear unless it crashed. Is that what happened? Metaldev (talk) 21:13, 26 September 2013 (UTC)

Launch date[edit]

Now, I'm currently very tired, as I haven't slept much lately, so I couldn't really focus on searching too intently for it, but I couldn't find mention of a launch date anywhere in the article. Is it just me and my tiredness, or has this article really overlooked that? The QBasicJedi 17:29, 24 June 2006 (UTC)

Cause of malfunction?[edit]

Article should state what exactly was the malfunction that caused the 11 minute burn and wrecked phase 2. Software bug? Stuck valve? Meters to feet conversion problem? (ouch, sorry) Tempshill 02:52, 9 April 2007 (UTC)

A member of the Clementine team told me it was a flaw in the spacecraft control software. I will look for a reference on the web. (talk) 18:27, 23 March 2012 (UTC)

Flaw in Clementine Software[edit]

From Crosslink. "Learning from Other People's Mistakes" by Paul Cheng and Patrick Smith Fall, 2007.

The computer onboard the Clementine spacecraft froze immediately after a thruster was commanded to fire. A "watchdog" algorithm designed to stop the thrusters from excessive firing could not execute, and Clementine's fuel ran out. The mission was lost.

From The Ganslee Grou . "Crash and Burn" Published in ESP, November 2000

Clementine, which very successfully mapped much of the moon from lunar orbit, was supposed to autonomously rendezvous with near-Earth asteroid 1620 Geographos. A software error caused a series of events that depleted the supply of hydrazine propellant, leaving the spacecraft spinning and unable to complete its mission.

From The University of Toledo. "Embedded Systems Software Reliability" by Walter W. Schilling, Jr.

While in operation, the Clementine orbiter itself can be classified as highly successful. However, problems were also occurring. During operation, over 3000 floating point exceptions were detected during execution, each of which was properly handled and logged. [Gan02] In order to continue the mission, ground controllers were required to perform hardware resets on the vehicle at least 16 times. [Lee94]

All of these problems came to a climax on May 7 as the 1750 system experienced yet another floating-point exception. However, unlike the previous cases, the exception was not handled properly by the software. Down linked data became random and nonsensical, and then the down linked data stream completely froze. Ground controllers attempted to revive the system by sending software-reset commands to the craft, but these were ignored. After 20 minutes, a successful hardware reset brought the Clementine probe back on line. [Lee94] However, all of the vehicle's hydrazine propellant had been expended. [Gan02]

In order to protect against random thruster firing, designers had implemented a software thruster timeout on the 1750 system. The intent of this safeguard was to shutdown the thrusters if excess firings were detected. However, in the case of the Clementine mission, this protection was defeated by a defect within the firmware. Evidence from the vehicle indicates that following the exception on the 1750 system, the microprocessor locked up due to a software defect. While in a this uncontrolled state, the processor erroneously turned on one or more thrusters, erroneously dumping fuel and imparting an 80 RPM spin on the craft. This thruster fired until the hydrazine propellant was exhausted or the hardware reset closes the valves that controlled the fuel flow to the thruster. [Gan02]

The 1750 contained a built in watchdog mechanism that could potentially detect run away source code and automatically reset the system. However, on the Clementine mission, software to control and use this feature was not implemented due to time constraints [Lee94].

Best Regards,

Hugh Pickens (talk) 18:52, 23 March 2012 (UTC)

Major embarrassment: picture upside down[edit]

The four pictures of the moon showing it from the four main directions, has a flaw. The picture File:Moon PIA00303.jpg is upside down. (You can check this out by mentally rotating it 180 degrees, and then comparing the edges of the adjacent pictures. Each picture should show some of the same patterns near the corresponding edge.)

I wrote this here for two reasons: The picture does not have a Talk page, and the error is most visible on this page, when you see the other pictures next to it. (talk) 23:21, 16 April 2013 (UTC)

Fixed. (You could have done this yourself by clicking the 'revert'-link on commons.) Buzz-tardis (talk) 13:59, 4 November 2014 (UTC)