Record Set For Space Laser Communication, Broadband in space Options

[RNeuhaus]

I have not found a proper topic in UMSF related to Space Technology improvement, so I picked up ones of Mars.

An interesant article about the successfull test of laser communication between the probe: Messenger and NASA's Goddard Geophysical and Astronomical Observatory in Maryland. MESSENGER was approximately 15 million miles (25 million km) away at the time.

Two-way laser communication in space has long been a goal for NASA because it would enable data transmission rates that are 10 to 1,000 times higher than traditional radio waves. While lasers and radio transmissions both travel at light-speed, lasers can pack more data. It’s similar to moving from a dial-up Internet connection to broadband

The Mars Telecommunications Orbiter spacecraft, set to launch in 2010, but cancelled last summer due to budget problems, would have used lasers to transmit data between Earth and Mars at a rate of between 1 to 30 million bits per second, depending on how close the two planets are to each other.

Currently, the maximum data rate between Earth and Mars is about 128,000 bits per second.

A major challenge with laser communications in space is keeping transmitter and receiver locked onto each other. This is like trying to aim the beam of a very strong laser pointer, akin to the type used in a conference room, at a target millions of miles away.

Radio waves radiate outwards from a transmitter in spherical ripples rather than pencil-thin beams like lasers. So the receiver and transmitter in a laser-based communication system have to be pointed very precisely.

In the other word, the major obstacle of laser telecomunications is a good aim between the transmitter and receiver. The case of Messenger is a great deed toward the use of laser telecomunications.

http://www.space.com/missionlaunches/060104_laser_comm.html

Rodolfo

[ermar]

It was mentioned briefly in the article, but a similar test was perfomed over a decade ago with the Galileo probe (albeit closer to Earth and only one-way communications rather than two). I got the chance to tour the Table Mountain Observatory this past summer, and the staffers there were still bragging that they had managed to beat out the New Mexico team on transmitting to Galileo!

[RNeuhaus]

Interesting article. The mentioned record is of 24 millions kilometers between Messenger and Earth and the case of Galileo, the conducted test was 600 thousands and up to 6 millions kilometers. Perhaps, the aborted project MTO, is going to comunicate between Mars and Earth in which distance varies between approx.70 and 378 millions kilometers.

I doubt about how to locate precisely the position of spacecraft before establishing the telecomunications. I suppose, previous to this, the space is located by the radar and then with the help of this will permit the laser to locate it with a high precision.

Rodolfo

[edstrick]

The first inter"planetary"s laser communication test was in 1967, when Surveyor 7, on the ejecta blanket of Tycho, imaged two (I think) of 3 or 4 laster beams aimed at it from Earth through astronomical telescopes.
Beams from cloud covered sites were not detected <no surprise!>, but beams from 2 sites with a clear shot to the moon were detected as very obvious unresolved bright points.

[algorimancer]

Slightly unrelated, but I've been wondering lately whether it would be feasible to use a military-grade high-intensity laser to "strobe" outer solar system objects for faster imaging and better spectrometry. I know that the lunar laser ranging project doesn't get many photons back, even with corner reflectors in place, but they're also not using a very large laser.

[ljk4-1]

The first inter"planetary"s laser communication test was in 1967, when Surveyor 7, on the ejecta blanket of Tycho, imaged two (I think) of 3 or 4 laster beams aimed at it from Earth through astronomical telescopes.
Beams from cloud covered sites were not detected <no surprise!>, but beams from 2 sites with a clear shot to the moon were detected as very obvious unresolved bright points.

And here is the actual image with a description, thanks to good ol' Exploring Space With a Camera:

http://history.nasa.gov/SP-168/section2a.htm#80

[tty]

Slightly unrelated, but I've been wondering lately whether it would be feasible to use a military-grade high-intensity laser to "strobe" outer solar system objects for faster imaging and better spectrometry.  I know that the lunar laser ranging project doesn't get many photons back, even with corner reflectors in place, but they're also not using a very large laser.

Interesting idea. The YAL-1A is getting close to full-scale flight testing and I don't see why they couldn't aim some of the systems tests at the Moon, Mars or whatever.
However I suppose that somebody with good academic credentials will have to write up a proposal.

tty

[Guest_BruceMoomaw_*]

Even before the cancellation of MTO, the Mars Decadal Roadmap committee in January was very uneasy about the expense of adding the laser com test to the mission. However, this technology certainly has a future at some point.