Questions tagged [ranging]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
5 votes
0 answers
168 views

What are the largest distances between two spacecraft that have been determined to a meter or so accuracy? How were these done?

This answer to Radio Telescope / DSN Node in L4 and/or L5 presents the challenge of implementing "very long" VLBI using the ~1 AU distance between Earth and a Sun-Earth triangular libration ...
2 votes
2 answers
1k views

Is there an anomalous variation of distance between Earth-Moon during a lunar eclipse?

Apart from normal (expected) variation of distance between Earth and Moon in any given time interval, what happens during a lunar eclipse by way of some unexpected (anomalous) deviation? Have lunar ...
3 votes
0 answers
54 views

Radio coherent transponders are the foundation of deep space navigation, have optical analogues been used? If so, the furthest distance measured?

Coherent radio transponders receive a signal from Earth containing specially encoded modulation, amplify it and retransmit it back to Earth. Correlating the received signal with the transmitted signal ...
1 vote
0 answers
55 views

Long delay-doppler measurements on deep space craft; couldn't optical measurements be made intermittently, mixed with contacts to other spacecraft?

In this comment below Will future deep space optical communications “ground stations” actually be in space, or on the ground? in response to a discussion about ground stations being used for tracking ...
5 votes
2 answers
527 views

How soon after "The Eagle" landed did they first attempt to bounce a laser off the Moon? When did it first succeed?

The question When did Houston figure out where the Eagle had landed? says (in part): During Apollo 11's stay on the surface, Michael Collins was given seven different locations to look for the ...
1 vote
0 answers
79 views

What was the first "bent pipe" or otherwise coherent transponder in deep space?

In this answer to On what basis is the information about the distance and velocity of the Voyager probes determined? in Astronomy SE I mentioned the term "bent pipe" transponder and also ...
3 votes
1 answer
101 views

How did LADEE and LDRC measure it's distance from Lunar orbit to Earth to 1 centimeter accuracy using optical communications?

The video Donald Cornwell plenary talk: NASA's Optical Communications Program: 2015 and Beyond was presented at SPIE Photonics West 2015. It's a great talk and worth the time. LADEE had [the Laser ...
2 votes
1 answer
179 views

When they shoot lasers at the Moon for ranging, what is the shape of the beam?

Laser ranging of the Moon is usually done with a Q-switched pulsed laser fed into a big (1 or 2 meter diameter) telescope as a collimator in order to get a tight beam all the way to the Moon in hopes ...
1 vote
0 answers
56 views

Parallax calculation

Given two points of observation on Earth (obs1=[lat1,lon1], obs2=[lat2,lon2]) and the apparent azimuth and altitude of a target from these two locations ...
10 votes
1 answer
1k views

How do ultra-stable oscillators for spacecraft work?

Many spacecraft carry "ultra-stable oscillators" for ranging and related measurements, but I can't quickly find any info on how these actually work. Are they just very pure quartz crystals, or do they ...
3 votes
2 answers
158 views

How to get an initial setting of the range gate for a Lunar Laser Ranging using a new Retro Reflector for the first time?

From an answer to this question They were searching by aiming their laser at the moon and looking for reflections. But the system is set to only detect photons in a very narrow range of ...