NASA to Develop GPS-Like System for the Moon
Written by Nancy Atkinson
During the second moonwalk of the Apollo 14 mission, Alan Shepard and Edgar Mitchell were hoping to walk to the 300 meter (1,000 feet) wide Cone Crater on the moon, not far from their landing site. However, the two astronauts were not able to find the crater's rim amid the rolling, repetitive terrain. Later analysis using pictures the two astronauts took determined they had come within 65 feet of the crater. People are used to having certain visual cues to judge distances, such as the size of a building or another car on the horizon, said Ron Li, who has been awarded a $1.2 million grant to develop a navigation system to be used on the moon. Since the moon has no landmarks or cues to help determine distance, getting lost, or misjudging a distant object's size and location would be easy, and extremely dangerous. New technology like sensors, inertial navigation systems, cameras, computer processors, and image processors will make the next trip to the moon easier for astronauts.
Li, from The Ohio State University, developed software for the Mars rovers Spirit and Opportunity, which has helped him learn a lot about navigation. The navigation system to help future astronauts find their way around moon won't use satellites; instead the system will rely on signals from a set of sensors including lunar beacons, stereo cameras, and orbital imaging sensors.
Images taken from orbit will be combined with images from the surface to create maps of lunar terrain. Motion sensors on lunar vehicles and on the astronauts themselves will allow computers to calculate their locations. Signals from lunar beacons, the lunar lander, and base stations will give astronauts a picture of their surroundings similar to what drivers see when using a GPS device on Earth. The researchers have named the entire system the Lunar Astronaut Spatial Orientation and Information System (LASOIS).
Astronauts will have a keypad and screen, possibly right on their spacesuits, to view their location and search for new destinations.
Keeping astronauts safe will be a top priority for Li's team, which includes experts in psychology and human-computer interaction as well as engineering.
"We will help with navigation, but also with astronauts' health as well," Li said. "We want them to avoid the stress of getting lost, or getting frustrated with the equipment. Lunar navigation isn't just a technology problem, it's also biomedical."
News Source: The Ohio State University
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July 21st, 2008 at 2:58 pm
I always thought this or something like it * would ultimately be a good idea for the Moon and other worlds, when there's a signifigant human presence…but wouldn't the Lunar mascons constantly mess up the satellites' orbits?
It only has to be a little bit, where navigation satellites are concerned, to degrade their accuracy.
* Perhaps low-frequency radio, like Loran or the old Omega system, if the dry lunar surface could propogate VLF signals halfway decently.
July 21st, 2008 at 5:25 pm
Since the moon has no atmosphere, all radio would be line of sight. On earth the atmosphere bends low frequency radio or it bounces from the ionosphere. I was thinking about GPS satelellights, but Frank is no doubt right in that the mass distribution would complicate precise position measurements.
At some point, perhaps very tall radio towers could be built so that two or three would be in sight for triangulation of position.
July 21st, 2008 at 6:09 pm
It would be cheaper to give each astronaut a deck of cards. When they get lost they can start playing solitaire on the ground and eventually another astronaut or n alien will come up behind them and tell them to put the 3 of clubs on the four of diamonds.
For a more high tech approach, Tetris on Gameboy has the same effect.
July 21st, 2008 at 11:43 pm
What are the chances of a single spot on the moon to get struck by an asteroid in, say, a 5-year period?
Isn't it a bad idea to build stuff on the moon?
July 22nd, 2008 at 1:10 am
James, vanishingly small. How often do we get asteroids hitting earth?
Micrometeorites are the significant problem, I would guess, and there are ways of dealing with those (e.g. don't build flimsy inflatable structures on the surface).
July 23rd, 2008 at 6:06 am
Why can't the "top side" of the existing earth orbiting GPS satellite system be used to navigate on the moon. There are more than enough satellites visible from the moon at any given moment to do the job. The RF easily and coherently reaches the moon for decoding. Of course it will be necessary to develop new hyper-sensitive GPS receivers and software that will interpret lunar surface position correctly. I suspect this approach will be dozens of times more economical than placing billions of dollars of satellite equipment in moon orbit.
July 23rd, 2008 at 8:46 am
Chances of getting hit by an asteroid on the moon are less than getting struck by lightning on earth. I would compare it more to how many satellites we have lost in earth's orbit due to an asteroid conjunction. The moon has no atmosphere, so asteroids don't burn up before reaching the surface.
The astronauts left various scientific instruments (mirrors, geological, etc) on the moon, and to my knowledge none of them have been destroyed by an asteroid… yet.
GPS satellite antennas are directed towards earth. While replacement satellites could be designed to transmit towards the moon only one satellite at a time would be useful. To properly triangulate a stationary location, you need to have at least 3 points separated by a certain amount of space; dependent upon how many points you actually use. Even though it is likely the moon could see 6-7 gps satellites at one time, they probably aren't spread out enough from the moons perspective to give an accurate reading.
Omega navigation (now I'm showing my age) isn't exactly the most accurate system available, and wouldn't be practicle for personal astronaut use, since VLF antennas need to be rather robust due to the large wavelengths. LORAN's different variations used different frequencies; and realistically was the basis for GPS. However, the transmitters are rather large! Not sure if they've gotten any smaller.
Technically, any of the systems can work. The major feat is to get transmitters in locations to triangulate positions. Without an atmosphere line of sight will have to be attained.