* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Home -> Astronomy News -> Mission News -> Laser Ranging Retroreflector
Post Info TOPIC: Laser Ranging Retroreflector
Blobrana


L

Posts: 131433
Date:
RE: Laser Ranging Retroreflector
Permalink  
 

Title: Long-term degradation of optical devices on the Moon
Authors: T. Murphy Jr., E. Adelberger, J. Battat, C. Hoyle, R. McMillan, E. Michelsen, R. Samad, C. Stubbs, H. Swanson

Forty years ago, Apollo astronauts placed the first of several retroreflector arrays on the lunar surface. Their continued usefulness for laser ranging might suggest that the lunar environment does not damage optical devices. However, new laser ranging data reveal that the efficiency of the three Apollo reflector arrays is now diminished by a factor of 10 at all lunar phases and by an additional factor of 10 when the lunar phase is near full Moon. These deficits did not exist in the earliest years of lunar ranging, indicating that the lunar environment damages optical equipment on the timescale of decades. Dust or abrasion on the front faces of the corner-cube prisms may be responsible, reducing their reflectivity and degrading their thermal performance when exposed to face-on sunlight at full Moon. These mechanisms can be tested using laboratory simulations and must be understood before designing equipment destined for the Moon.

Source

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Dusty mirrors on the moon obscure tests of relativity

The Apollo astronauts knew that moon dust was troublesome stuff. Now that dust could limit our ability to find cracks in Einstein's general theory of relativity.
Many of our best tests of relativity come from lunar ranging experiments. Several times a month, teams of astronomers from three observatories blast the moon with pulses of light from a powerful laser and wait for the reflections from a network of mirrors placed on the lunar surface by the Apollo 11, 14 and 15 missions, as well as two Soviet Lunokhod landers. By timing the light's round trip, they can pinpoint the distance to the moon with an accuracy of around a millimetre - a measurement so precise that it has the potential to reveal problems with general relativity.
Read more

__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Each clear night when the moon is high in the sky, a group of astronomers in New Mexico take aim at our celestial neighbour and blast it repeatedly with pulses of light from a powerful laser. They target suitcase-sized reflectors left on the lunar surface by the Apollo 11, 14 and 15 missions, as well as by two Russian landers.
Out of every 300 quadrillion (10^15) photons that are sent to the moon, about five find their way back. The rest are lost to our atmosphere, or miss the lunar reflectors altogether.
From this small catch, the team can assess the movement of the moon to an accuracy of a millimetre or two - a measurement so precise that it has the potential to show up any cracks in Einstein's general theory of relativity. If that's what it does, this lunar laser-ranging experiment (LRRR) will become Apollo's greatest scientific legacy.

Read more

__________________
Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.
Home -> Astronomy News -> Mission News -> Laser Ranging Retroreflector


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard