A large array of hundreds of telescope modules programmed to detect very low frequency radio waves will be placed on the far side of the moon. Covering an area of approximately two square kilometers, the telescopes will be put into place by robotic vehicles.
The Lunar Array for Radio Cosmology (LARC) is a joint project of NASA and ten scientists from MIT’s Kavli Institute for Astrophysics and Space Science. The goal of the project is to learn about the period of time just after the big bang when stars, star clusters and galaxies formed over a billion year period.
The big advantage in using the dark side of the moon, an area where made-made transmissions from Earth never reach, is avoidance of interference from Earth. Specifically, Earth’s ionosphere that contains electrically charged particles that would interfere with Earth based telescopes will be avoided, and the electromagnetic radiation produced by Earth’s ubiquitous array of radio and television stations will be blocked. Since low frequency emissions have long wavelengths, the telescopes need not be precisely positioned in order to gather the radio waves. Lunar dust, which might normally be a problem, will not be something that would impair the functioning of the telescopes. Data collected would test current theories of formation and evolution of the universe, particularly cosmic inflation. A secondary benefit would be to study coronal mass ejections from the Sun, which from time to time interrupt telecommunications on Earth and can interfere with satellite functionality. Construction would not begin until 2025 and would cost 1 billion dollars or more. NASA is awarding a $500,000 grant to develop a plan for deployment to the MIT team as well as a second team from the Naval Research Laboratory working independently on a similar plan.
Jacqueline Hewitt, director of MIT’s Kavli Institute for Astrophysics and Space Science, stands behind a prototype of a radio telescope array planned for the far side of the moon.
Jacqueline Hewitt, a researcher with MIT, spoke with Joe Palca on NPR’s Science Friday radio program regarding the project. The audio should be available soon here.
February 22, 2008 at 4:00 pm
I listened to Ms. Hewitt talking about LARC on NPR today and had a question I was hoping someone would ask but didn’t. Since the array will be on “dark” side of the moon how do plan to transmit data from the telescope since it won’t be in direct sight of the earth?
Thanks!
Marc
February 22, 2008 at 4:18 pm
A very good question Marc!
I assume that the spacecraft that will be dropping these telescopes down to the surface of the moon will remain in orbit around the moon and serve as the relay for transmitting the information back to Earth.
Bill
February 28, 2008 at 12:40 am
That is interesting. I was watching a series documentary on the History channel that comes on every Tuesday called The Universe. During an episode about space travel, one high ranking NASA officer stated that after the Appollo disaster, manned flights outside the orbit of the Earth were basically cancelled indefinately. Even if they wanted to send a person on another world, they don’t have the funding anymore. Plus, the reusable spacraft, such as the Endeavor are aging, and aren’t that reliable anymore. So, that is probably why we are sending out probes to Mars, and these robots to the far side of the Moon, instead of having people do it.
“1 grain of dust,” stated the officer, “traveling at supersonic speeds in space, can hit an astronaught in a way that is comperable to being hit by a dumptruck at 65 miles an hour.”
They even showed holes and dents and cracked windows as the result of debris hitting the spaceshuttles while in orbit, you could probably google them if you want to find them.
February 28, 2008 at 12:55 am
Hey James,
Good point about the grain of dust. I’m skeptical that even if we could travel at the speed of light that unless there is some kind of force field in front of the craft to scoop the cosmic dust out of the way, like an old train engine could scoop animals off the track, there is no way a spacecraft could survive. The dust is sparse in space but when you travel that fast you are compressing space ahead of you and a little dust over a large area could add up to a brick wall!
March 5, 2008 at 10:20 am
I’m not even sufficiently familiar with the use of weblogs to distinguish questions from answers, so I can’t tell if what I wish to ask has been answered already. I can think of two ways to sum the individual signal components received by all the elements of the radiotelescope array: 1. at each element, convert the received (analog) signal to a digital signal, have that signal modulate a high-frequency carrier, and transmit it through space to an orbiting relay station that sums the signals and re-transmits that summed signal to Earth or re-transmits all the components for summing on Earth, or 2. sum the individual components while they are still in the analog domain, for example by relaying them over long optical fiber links to a central station on the surface where the summed analog signal is converted to the digital domain and relayed to orbit and then to Earth as in scenario 1. This second scenario seems messier because of the optical fiber links, but does not require as much signal processing equipment at the individual telescope elements, which must receive some “synch”-ing oscillation signal to preserve the received signal phases through the frequency down-conversion and A/D conversion processes. Are either of these scenarios close to what is being envisioned?
March 5, 2008 at 1:21 pm
Hi Ed,
I don’t think they know yet but I agree with you. I would think it would be your option #1. NASA has awarded a grant of $500,000 to MIT and a second team at the Naval Research Laboratory to develop the proposal which would have the details of how this would be set up. I didn’t see a timeline when this would be complete, probably after a year or so.
June 12, 2009 at 1:28 pm
Long-baseline radio astronomy on and near the earth is a mature field. They have well-developed methods of recording the data from the individual telescopes, storing it, and analyzing it later. A key element is the use of a local oscillator that can be locked to cesium clocks or equivalent; this allows each station to be stand-alone, working independently during data taking, and only synchronizing a few times around the time of observation. Later, in an office somewhere, the analyst performs interferometric analysis of the data from data tapes, CDs, or whatever. This entails synchronizing the time sequences from each telescope and fitting a source model to those observations. This is almost certainly how it would be done from the moon.
Though we’re familiar with pictures of the VLA in Arizona, where all the radio dishes are within sight of each other, an earth-spanning array of radio telescopes, known as a VLBI array, has been successfully used for several decades. And VLBA (adding a space antenna) could be used with some modest investment. Those telescopes don’t have to see each other; they just need to observe the same object simultaneously and have good stable synchronized clocks.
This is unlike optical interferometry, where pairwise beam combination and detection must occur immediately and with great care and handling of the beams. Optical interferometry from space and the moon is more of a challenge as a result.
June 12, 2009 at 1:33 pm
Oops, sorry, VLA is in Socorro, NM