Chang'e-4 farside landing mission |
Chang'e-4 farside landing mission |
Jul 15 2015, 01:35 PM
Post
#1
|
|
Junior Member Group: Members Posts: 31 Joined: 10-January 14 Member No.: 7094 |
Preliminary Suggestions for International Cooperation on Chang'E-4 Lunar Probe Xu Y. (China) http://www.unoosa.org/pdf/pres/copuos2015/...2015tech08E.pdf An Introduction of Chang’E-4 Probe: Probe(Lander,Rover)+ Relay Statellite Soft-landing on lunar farside Landing and roving exploration Will be launched between 2018 and 2019 the probe: Chang’E-4 probe,lander and rover have the same technical status with the Chang’E -3; but exploration will be redesigned; the payload will be reconfigered; The name of the probe might be changed. Chang’E-4 probe is a backup spacecraft of Chang’E -3 probe. By now, all platform products of the probe have been manufactured, waiting for further AIT. The probe will be launched by a long March 3B rocket from the Xichang Statellite Launch Center(XSLC) which is the same way with the Chang'E-3 between 2018 and 2019 The relay statellite: will be first launched into a lunar transfer orbit about the end of 2018 in the whole mission, then starts its earth-to-moon jurnery alone, and will enter and run in a Halo orbit around the Earth-Moon L2 point; the design life is 3 years. would provide relay service for the probe and the Earth, and carry out exploration. Engineering objectives are as follow. To realize the first soft landing on the lunar farside and perform exploration in human history. To demonstrate technologies of lunar data relay, landing and roving on complicated terrains of the lunar farside, and lunar night power generation; To perform further detailed survey on lunar environment in order to lay a foundation for subsequent lunar exploration mission. Tentative Scientific objectives are as follow. To study lunar surface dust features and its formation mechanism; To perform in-situ measurement of lunar surface residual magnetism and study its interaction with solar wind; To study lunar surface temperature and particle radiation environment; To perform lunar surface topology and material composition analysis, shallow-layer structure survey and study; To explore and study lunar interior structure of spheres; To perform lunar based VLF astronomical observation and study |
|
|
Dec 20 2018, 09:13 PM
Post
#2
|
|
Senior Member Group: Members Posts: 2106 Joined: 13-February 10 From: Ontario Member No.: 5221 |
Thanks for the explanation Phil...I should have thought a bit more about the geometry!
I wonder if they will attempt another video of the landing, if the bandwidth is good enough. The Chang'E 3 footage was amazing! Incidentally, I checked, and there is a slightly longer signal delay through the relay satellite (about 0.4 seconds) than there would be for a near side landing (since signal needs to travel to the Lagrange point past the Moon, the far side surface, and then back again.) |
|
|
Dec 30 2018, 06:01 PM
Post
#3
|
|
Member Group: Members Posts: 127 Joined: 3-September 12 From: Almeria, SE Spain Member No.: 6632 |
Hi all!
Cháng'é-4 is now in the final 15x100km orbit! https://gbtimes.com/change-4-lowers-orbit-r...ide-of-the-moon Very nice video there! I herewith dare to predict the landing time: 02 January, 00:00 UTC (midnight) at 178.1° East. How do I get there? Quite simple calculations with the publicly available data: First looking at the orbital plane: Lunar orbit insertion (LOI) was on 12Dec at 08:39 (all times UTC) in (- assumption! -) a plane exactly perpendicular to the earth vector, this means "face-on" and over the poles. Furthermore: Landing site: Between 176.4° and 178.7° East. (This is from here.) The orbital plane therefore has to rotate between LOI and landing between 271.3° and 273.6°. Or, more precisely, the Moon under it. Since a sidereal lunar rotation lasts 27.3217 days, this corresponds to a time from LOI to landing of 20.590 and 20.764 days. That falls between 01Jan 22:48 and 02Jan 02:59 (as said, UTC). That's a period of just over 4 hours, enough for two passes. And now, when exactly? The insertion into the final orbit of 15x100km was early today (30Dec) at 0:55 UTC. This injection occurs in the aposelene, this means half an orbit from periselene! And the periselene is logically (almost) over the landing site. The orbital period can be calculated (113.68min), so you just have to look when a multiple-plus-zero-point-five of the orbit period falls into the the time frame calculated above. This is the case (UTC) on 01 Jan at 23:58 (37.5rev) and on 02 Jan at 01:51 (38.5rev). With uncertainty in the minute range and a bit of time for the final (slow) approach, it will be midnight UTC on January 2nd. And the backup opportunity at 177.0° East just before 2h UTC. To all this also fits that on that day, the Moon in Beijing rises at 03:45 (Beijing time). The landing would be at 07:58, the backup landing at 09:51, and the moonset at 14:23. Perfect timing for the ground stations. Some (dis-)agreement here? Best Thorsten |
|
|
Lo-Fi Version | Time is now: 26th September 2024 - 12:57 PM |
RULES AND GUIDELINES Please read the Forum Rules and Guidelines before posting. IMAGE COPYRIGHT |
OPINIONS AND MODERATION Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators. |
SUPPORT THE FORUM Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member. |