Talk:MESSENGER

What is causing the orbital decay?

In earth orbit, atmospheric drag is the only significant reason that orbits decay. Mercury has an almost nonexistent atmosphere, so what is preventing Messenger from continuing to orbit for centuries? 199.46.196.230 (talk) 00:03, 30 April 2015 (UTC)

It is the Sun's gravity that distorts its orbit: [1]. Cheers, BatteryIncluded (talk) 01:31, 30 April 2015 (UTC)

BTW, is it known if there are any stable orbits around Mercury? Messenger has had a very elliptic orbit, after all. --Roentgenium111 (talk) 12:14, 30 April 2015 (UTC)

"'Following this last maneuver, we will finally declare the spacecraft out of propellant, as this maneuver will deplete nearly all of our remaining helium gas,' said Daniel O’Shaughnessy, mission systems engineer at APL. 'At that point, the spacecraft will no longer be capable of fighting the downward push of the sun's gravity.'"

This is a poorly-worded explanation, as the sun's gravity pulls objects toward the center of the sun; it does not impart a "downward push." Is a more rigorous explanation available? Thanks 199.46.200.232 (talk) 17:45, 30 April 2015 (UTC)

So the Sun's gravity was reducing MESSENGER's periapsis? --JorisvS (talk) 09:24, 1 May 2015 (UTC)

How about this explanation? - http://messenger.jhuapl.edu/qa/index.php?faq=1&ca=36#qn581 ghouston (talk) 09:28, 1 May 2015 (UTC)

"Because of gravitational perturbations by the Sun, the orbit of the spacecraft around Mercury is constantly drifting toward lower periapse"

Nope... that is a restatement of the assertion that the Sun's gravity took energy out of Messenger's orbit; but still does not explain the mechanism by which it did so. At least it did not use bogus phrases like "downward push." 199.46.200.231 (talk) 23:12, 7 May 2015 (UTC)

So then go to the Applied Physic Laboratory web forum and tell them they are wrong: [2] [3][4]. BatteryIncluded (talk) 23:21, 7 May 2015 (UTC)

Actually, your first source states that solar perturbations increased the minimum altitude in the first two years, before reducing it in the later years, and gives a more detailed explanation:

"Throughout the orbital mission, the orbital line of apsides, which connects the orbit's lowest and highest points, rotates clockwise around Mercury. The argument of periapsis (ω) is the angle between the northerly crossing of Mercury's equatorial plane and the minimum-altitude end of the line of apsides, as measured in the spacecraft's orbit plane. When ω is greater than 90°, the strongest gravitational forces that act on the spacecraft's trajectory, those due to Mercury and the Sun, increase the spacecraft's minimum altitude and shift the tilt (inclination) of the orbit closer to passing over the north and south poles. The argument of periapsis reached 90° on 6 March 2013, just prior to the end of MESSENGER’s first extended mission. As the argument of periapsis decreased below 90°, the spacecraft orbit's inclination decreased (moved toward the equatorial plane) and the minimum altitude decreased. " --Roentgenium111 (talk) 15:30, 8 May 2015 (UTC)

That sounds rather authoritative. Thank you, Roentgenium111, for digging up this tidbit from the fascinating and sometimes counterintuitive world of orbital perturbations.

It sounds like, if perihermion had been higher, Messenger could have carried on this dance for centuries -- with the solar perturbation causing perihermion to tend to increase half of the time, and causing it to tend to decrease the other half of the time. GPS Pilot (talk) 17:30, 21 January 2018 (UTC)

Without walking through the math on it, one concept related to this is the Hill sphere, and Mercury has a small one. It is complicated by its eccentric orbit. Years ago I did work out that geosynchronous orbits on Mercury are impossible, but that is mainly due to the planet's slow rotation. Also, gravity results from MESSENGER indicate that at least some of Mercury's large impact basins have mascons, and these are known to disrupt orbital stability on the moon. So the planet's eccentric orbit and proximity to the sun reduce the probability of stable high orbits and the mascons reduce it for low orbits. Jstuby (talk) 11:53, 27 March 2023 (UTC)

Perihermion units ?

118.4 what? Presumably either miles or km.

Thermal design

Could note the use of phase change paraffin wax packs to control/limit camera temperatures - as in thermomechanical design section of [5] - Rod57 (talk) 13:52, 11 September 2017 (UTC)

"Avoid writing with all caps"

That's a quote from MOS:ALLCAPS. Why is this rule ignored for this article? - 91.10.52.4 (talk) 18:19, 25 January 2018 (UTC)

MESSENGER is a backronym for Mercury Surface, Space Environment, Geochemistry, and Ranging. BatteryIncluded (talk) 19:27, 25 January 2018 (UTC)

That would make sense, if anyone ever used "Messenger" as a Backronym, ever. Very clearly everyone calls it "Messenger", not M. E. S. S. E. N. G. E. R. - 91.10.52.4 (talk) 21:05, 25 January 2018 (UTC)

Since NASA conceived it, developed it, built it, and launched it, they can call it anything they want. They chose MESSENGER in all caps: http://messenger.jhuapl.edu/

That is that. Cheers, BatteryIncluded (talk) 00:16, 26 January 2018 (UTC)

That is most certainly not that, and I wonder where that sentiment comes from.

Wikipedia has no obligation to follow marketing or other considerations applied by creators. Non whatsoever. That's why rules like MOS:ALLCAPS take precedence over the wishes of NASA. - 91.10.54.18 (talk) 07:41, 26 January 2018 (UTC)

Ironic you write NASA with all caps. Relax. BatteryIncluded (talk) 14:28, 26 January 2018 (UTC)

In the header of Wikipedia:Manual of Style/Capital letters, it states "Wikipedia relies on sources to determine what is conventionally capitalized; only words and phrases that are consistently capitalized in a substantial majority of independent, reliable sources are capitalized in Wikipedia.". Peer reviewed journals are among the most respected independent sources. If you type "mercury messenger" (without the quotes) into Google scholar, you'll see that every reference on the first three pages (as many as I checked) is all caps.

Also, the very first sentence of Wikipedia:Manual of Style/Capital letters it says: "This guideline is a part of the English Wikipedia's Manual of Style. It is a generally accepted standard that editors should attempt to follow, though it is best treated with common sense, and occasional exceptions may apply." So it's a guideline, and not a rule.

And most important, it's best for the reader. Anyone who reads about this anywhere else will find it in all caps (with overwhelming probability). When they come to Wikipedia for more information, it should be in the form they saw it elsewhere; otherwise takes mental effort and jars the reading flow. Likewise, if they read about it first here, they should not be surprised to see it in all caps in other sources they may check. LouScheffer (talk) 13:10, 26 January 2018 (UTC)

First object on Mercury?

Is Messenger the first man-made object on Mercury? — Preceding unsigned comment added by 92.6.238.148 (talk) 15:42, 13 April 2019 (UTC)

Yes, the wreckage is. Jstuby (talk) 11:42, 27 March 2023 (UTC)