MRO Telecommunications |
MRO Telecommunications |
Guest_AlexBlackwell_* |
Sep 26 2006, 12:06 AM
Post
#1
|
Guests |
There's a new presentation entitled "Mars Reconnaissance Orbiter Telecommunications" on the JPL DESCANSO Design & Performance Summary Series web page (scroll to the bottom).
|
|
|
Sep 26 2006, 03:50 PM
Post
#2
|
|
Member Group: Members Posts: 105 Joined: 13-July 05 From: The Hague, NL Member No.: 434 |
I hope it is sufficiently understood by all that there is a major inconvenience with the outage of DSS 55 near Madrid: http://www.space.com/news/060802_dsn_problems.html.
Till January 2007 according to this article. Probably a significant impact on HIRISE I would guess, but as the article states: the DSS teams have plenty of experience in delivering the impossible. Let us hope they will find a workaround this time as well. |
|
|
Sep 26 2006, 03:59 PM
Post
#3
|
|
Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
An impact - but not a HUGE one - most of the downlink for MRO is 34m based. There are 14 Xband 35m passes per week, and only 3 70m passes. Yes - higher speed with the 70m, but given that it's only 3 passes, they can be offset away from the down-dish.
Colin Clark should be picked up on this one... "a result of a longer than planned shutdown of one of the three antennas that comprise Deep Space Network (DSN)," The DSN is only 3 dishes is it Colin?... that's just lazy journalism..Each of the three sites has at least four dishes, and a total of 15 I believe. However there is no doubt that the DSN is in need of serious investment - a good case could be made for several more 35m's at each site - that could be used in an array ( as has already been demonstrated ) for the typical 70m requirements. A concerted effort across the whole network (perhaps even internationally) to build perhaps 6 or 9 identical dishes to reduce costs would be a wise move. Doug |
|
|
Sep 27 2006, 02:37 AM
Post
#4
|
|
Member Group: Members Posts: 234 Joined: 8-May 05 Member No.: 381 |
What JPL would like to build is an array of 400 antennas, each 12 meters in diameter, at each of the three
DSN sites. This would "increase downlink capability of DSN by two or three orders of magnitude". It would also have the obvious advantage of "graceful degradation" if one antenna would fail. Such an array would benefit every deep space mission, including MRO, but imagine what it would mean to New Horizons Pluto spacecraft. It might increase communications distance enough to add a few more KBO's to the encounter list. One paper discussing this type of antenna array technology is at: tmo.jpl.nasa.gov/progress_report/42-160/160B.pdf This technology is certainly closer to implementation than optical communications ! You'd also see improved data rates long before all 400 would be deployed. |
|
|
Sep 27 2006, 07:21 AM
Post
#5
|
|
Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
What JPL would like to build is an array of 400 antennas, each 12 meters in diameter, at each of the three DSN sites. Rather than dumping all the eggs in single locations it would be useful if this exercise also extended it's brief a bit so that each of the three main sites had a backup at a similar longitude but was located in a zone with a very different climate to the primary site. For example Madrid could be paired with a South African site, Goldstone with a South American one and Canberra with someplace in Siberia. That way we'd have a practical "hot spare" environment. It's not a cheap thing to try and implement but I believe that the global part of the Square Kilometer Array radio telescope project has these sort of requirements. I really do think that the SKA is a wonderful project but surely the DSN is more important? |
|
|
Sep 27 2006, 09:46 AM
Post
#6
|
|
Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
There was a South African DSN site, but that was abandoned during the sanctions era against the apartheid government. There should be paired DSN stations, one north, one south for each of the 3 longitude zones.
|
|
|
Sep 27 2006, 09:57 AM
Post
#7
|
|
Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
If you do the maths, and I'm sure it's just an accountants and engineers xls file that will do it..
For a given aperture you need either A large number of small cheap dishes with a complex interconnection system A small number of larger more expensive dishes with a less complex interconnection system i.e. there's will be a graph - with points between 1 x 100 metre dish, and 10,000 x 1 metre dishes where the cheapest option exists....the challenge is to find that point, make it as easily deployable as possible, and then build it - or subsets of it, at various locations. Doug |
|
|
Sep 27 2006, 03:47 PM
Post
#8
|
|
Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
A good engineer, looks for the best equilibrium between few and large dishes and many and small dishes. However, anyway, there is a tendency that the future, the many and small dishes will be winner due to its advantages of redundancies required to meet to the increasing number of spacecraft navigating in the space. The time will dictate the best equilibrium.
Rodolfo |
|
|
Sep 27 2006, 08:51 PM
Post
#9
|
|
Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
I had a post related in a way to this issue a couple of days ago here. Earth-Sun Trojan DSN relay satellites, anyone?
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
|
|
|
Sep 27 2006, 09:00 PM
Post
#10
|
|
Senior Member Group: Members Posts: 1636 Joined: 9-May 05 From: Lima, Peru Member No.: 385 |
I had a post related in a way to this issue a couple of days ago here. Earth-Sun Trojan DSN relay satellites, anyone? Your idea is brillant. This will eventually be justified their costs to build, send and operate relays satellites in the Lagrange points L4 and L5 only when the number of spacecraft operating abroad in space is overhelming. That will happen in some future day! On the other hand, the relay satellites at the good Lagrange point is not related to the problem of the traffic of messages (more DSN) but it only is good for avoiding the telecommunications during any superior conjunction. I might be wrong! but it is anyway an interesting topic. Rodolfo |
|
|
Sep 28 2006, 12:14 AM
Post
#11
|
|
Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Thanks, Rodolfo. Always knew I was born 200 years too early!
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
|
|
|
Sep 28 2006, 09:33 AM
Post
#12
|
|
Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
Ahem...
Look for George O. Smith's "Venus Equilateral"a book of stories by radio engineer George O. Smith, copyright 1942. "The Venus Equilateral Relay Station was a modern miracle of engineering if you liked to believe the books. Actually, Venus Equilateral was an asteroid that had been shoved into its orbit about the Sun, forming a practical demonstration of he equilateral triangle solution of the Three Moving Bodies. It was a long cylinder, about three miles in length by about a mile in diameter... This was the center of Interplanetary Communications. This was the main office. It was the heart of the Solar System's communication line, and as such, it was well manned. Orders for everything emanated from Venus Equilateral." (found with a google for "Venus Equilateral") |
|
|
Sep 28 2006, 02:21 PM
Post
#13
|
|
Merciless Robot Group: Admin Posts: 8783 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
Never read it...bummer...thought I had an original idea, there! Oh, well, fame and fortune remain elusive...
Within the framework of current technology, these Trojan relay sats could be linked to Earth-orbiting intermediate satellites in orbits (precessing "semi-Sun-synchronous" polar?) that would provide a continuous LOS path to them; in turn, you could use MUCH smaller (even commercial-off-the-shelf) ground stations & deploy a lot of them in order to maintain continuous contact. -------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
|
|
|
Sep 28 2006, 02:26 PM
Post
#14
|
|
Founder Group: Chairman Posts: 14432 Joined: 8-February 04 Member No.: 1 |
You mean take TDRS and turn it interplanetary.
Doug |
|
|
Sep 29 2006, 03:41 AM
Post
#15
|
|
Member Group: Members Posts: 599 Joined: 26-August 05 Member No.: 476 |
An aerospace engineering student at my alma mater wrote a paper in early 90's on Mars relay sats in halo orbits around the L1 and L2 points. Two satellites would provide near-continuous global coverage of Mars. The downside is that the greater distance between Mars and L1/L2 required the comm systems on Mars to be higher powered / use bigger antennas compared to that required by low Mars orbit relays. Tradeoff between coverage time and power / structure.
|
|
|
Lo-Fi Version | Time is now: 27th April 2024 - 12:44 AM |
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. |