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Questions tagged [delay-doppler]

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1 vote
1 answer
76 views

Calculating change to radio signal propagating around via satellite orbits

What is the best way to calculate either the time difference or frequency change for a radio signal in the following scenario? 60 satellites are in the same circular orbital path at 6 degree intervals....
2 votes
1 answer
51 views

Satellite Navigation: Measuring Velocity & Position

How is the position and velocity of a satellite measured from ground? Radar measurements could give us range and range rate which are scalar quantities (if I understand this correctly). But how could ...
5 votes
0 answers
169 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 ...
3 votes
0 answers
58 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
56 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 ...
2 votes
1 answer
548 views

Analyse the Doppler effect in non-GEO satellites: calculation of Doppler shift ( frequency)

I want to compute the Doppler frequency for LEO/MEO/GEO satellites. For the calculation I am using the following equations: $$V= \sqrt{(G \cdot \frac{M}{R+h})}$$ - satellite speed. Height dependent $...
7 votes
1 answer
243 views

Has Same Beam Interference (SBI) been used or at least tested at Mars? Are there plans to use it in the next few years?

Question: Has Same Beam Interference (SBI) been used or at least tested at Mars? Are there plans to use it in the next few years? Considering that there's already some orbiters and landers and rovers ...
9 votes
0 answers
198 views

Was the Doppler shift of InSight's "tone" measured and plotted somewhere?

I watched a YouTube live broadcast from the InSight mission control area and saw lots of images of happy people cheering and jumping up and down, which is great! If it wasn't 4 AM where I was I might ...
3 votes
1 answer
249 views

What does Cees Bassa's Doppler plot of Chandrayaan 2 show?

Cees Bassa's tweet shows a plot of received frequency versus time, with the Doppler shift of the Moon's center of mass subtracted. For a lunar orbit the resulting plot would show sinusoidal-like ...
3 votes
0 answers
110 views

Understanding shape of DSN's 'kinky uplink protocol' keeping frequency in coherent transponder's optimum bandpass?

This tweet by deep space SDR enthusiast and amateur radio operator Edgar Kaiser @df2mz shows a squiggly tone from MRO. Mars Reconnaiscance Orbiter (MRO) X-band downlink. The signal shows this ...
4 votes
1 answer
225 views

How many solar system bodies have had coherent radio transponders?

A transponder amplifies, (often) frequency-shifts, and rebroadcasts a received signal. Old-style telephone and TV distribution satellites in GEO used simple transponders to rebroadcast the uplinked ...
4 votes
1 answer
177 views

How does a third DSN station serves as a “relay” to tie-together observations by two other stations doing VLBI?

Section 2.1 of the DESCANSO document 211 Wideband Very-Long Baseline Interferometry (from here, found here) says: The precision of a VLBI measurement improves with the length of the baseline. The ...
2 votes
1 answer
241 views

Have any deep-space spacecraft supported same-band turnaround of Earth-based doppler measurements?

Table 1 of DSN Telecommunications Link Design Handbook, 201, Rev. B, Frequency and Channel Assignments gives Spacecraft Transponder Turnaround Ratios that are supported by the Deep Space Network. ...
1 vote
1 answer
949 views

What are the differences (if any) between the techniques of range-rate and delay-doppler measurements?

This answer to How does an onboard atomic clock help interplanetary navigation? says: Range-Rate is the two-way measurement of signals broadcast from one location on Earth, received and retransmitted ...
1 vote
0 answers
80 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
2 answers
2k views

Delay-Doppler maps in space science

Maybe this question might be more physics related, but I've read about mostly in context of space science: What is a delay-doppler map (DDM)? I can find it in exploration of asteroids (e.g. (...
4 votes
1 answer
505 views

Is delay-doppler radar imaging of NEO asteroids possible only if it spins fast enough?

Emily Lakdawalla's blog on the Planetary Society's page explains some of the basic principles in the delay-doppler radar imaging of asteroids, and other astronomical bodies by extension. Radar from a ...
4 votes
2 answers
319 views

Has there ever been an instance of asteroid discovery by radar; seen first by radar rather than being observed after optical discovery?

In a discussion below this answer to Can we use something like RADAR to detect asteroids? I'm complaining that the answer is essentially wrong; Yes, radar is one of the useful tools for detecting and ...
6 votes
0 answers
218 views

What can be learned from NASA's choice of Didymos B for the Double Asteroid Redirection Test

The NASA News item NASA’S First Asteroid Deflection Mission Enters Next Design Phase describes a test the kinetic impactor technique that could someday be used to adjust the orbit of an asteroid in ...
4 votes
2 answers
250 views

How does Deep Space Network's DSS-14 transmit radar and receive it at (almost) the same time? (monostatic radar)

@Hobbes' concise yet thorough answer to the question What are monostatic radar observations, and how will Deep Space Network's DSS-13 be used to observe asteroid 1999 WK4's flyby of Earth? tells us ...
3 votes
1 answer
103 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 ...
0 votes
1 answer
95 views

What are monostatic radar observations, and how will Deep Space Network's DSS-13 be used to observe asteroid 1999 WK4's flyby of Earth?

NASA JPL page https://echo.jpl.nasa.gov/asteroids/1999KW4/1999KW4_planning.2019.html says of the radar observations during the close approach of asteroid 1994 KW4 (in part): Update on 2019 May 22: A ...
2 votes
1 answer
347 views

How exactly does TDRSS provide tracking? (Tracking and Data Relay Satellite System)

This excellent answer to How does satellites know it is in apogee or perigee states: The NASA Tracking and Data Relay Satellite System (TDRSS) adds to this a constellation of satellites in such a ...
3 votes
1 answer
221 views

3D celestial puzzler; why InSight's two RISE horns point slightly south of east, and north of west?

note: possibly helpful: LaRa after RISE: Expected improvement in the Mars rotation and interior models Contraindre la structure interne de Mars avec GINS @karthikeyan's excellent answer links to ...
3 votes
1 answer
109 views

Farthest distance to a solar system object that's been determined by spacecraft transponder?

Bouncing radar off of Venus' surface has yielded a rich body of data about the planet. Based on Venus' aphelion and Earth's perihelion, we know then that the answer is at least 38 million kilometers ...
2 votes
1 answer
391 views

Farthest distance to a solar system object that's been measured by radar?

Bouncing radar off of Venus' surface has yielded a rich body of data about the planet. Based on Venus' aphelion and Earth's perihelion, we know then that the answer is at least 38 million kilometers ...
2 votes
0 answers
182 views

Separating fact from fiction, how to get from this radar image to this GIF?

The NBC News article Mile-wide asteroid and its tiny moon to zoom past Earth this weekend; Dubbed 1999 KW4, the "binary" space rock will skim past our planet harmlessly at a distance of 3 million ...
2 votes
1 answer
275 views

How will InSight's RISE antennas end up pointed in the right direction?

The rendering of InSight shows the RISE antennas, the two microwave horns pointed just above the horizontal over each of the solar array paddles. If I understand correctly the experiment works when ...
6 votes
1 answer
788 views

How does a three-way doppler shift measurement work?

I was looking at this document who's name I can only speculate. Its title and designation includes: 810-005, Rev. E, 201, Rev. B, DSN Telecommunications Link, Design Handbook, 201, Rev. B, Frequency ...
0 votes
1 answer
56 views

Is 2012 TC4 part of the Near-Earth Object Human Space Flight Accessible Targets Study?

This nifty answer describes and provides links to the data of the recovery of near earth object 2012 TC4, and the answer also shows the first actual image of the body for this pass. At apparent ...
10 votes
1 answer
1k views

Why do radar maps of the surface of Venus have missing slices?

The visually opaque clouds of Venus still pass radio and some microwaves, and so powerful radar signals can be used to map the surface. This is probably done using some kind of delay-Doppler technique,...