Questions tagged [radar]

Radio detection and ranging devices. Operate by detecting and processing return echoes from objects and surfaces of signals at radio frequencies. Can be used to ascertain spatial coordinates and velocities, surface characteristics, object orientation, aid in object identification. In space applications used for tracking, radar imaging, rendezvous, collision avoidance, and other purposes.

Filter by
Sorted by
Tagged with
1 vote
1 answer
151 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 ...
user avatar
  • 148k
3 votes
0 answers
50 views

Has Perseverance fired up its RIMFAX yet?

PIA24048: Testing RIMFAX for NASA's Perseverance Rover Original Caption Released with Image: A test model of the RIMFAX instrument — aboard the trailer behind the snow mobile — undergoes field ...
user avatar
  • 148k
0 votes
1 answer
120 views

Does transmitting from a few dishes significantly improve the performance of radar surveillance from Earth at GEO and beyond? If so, how exactly?

The BBC's US wants giant radar in UK to track space objects says: Lt Col Jack Walker of the US Space Force told the BBC the US was "in discussion" with the UK about putting the radars "...
user avatar
  • 148k
3 votes
2 answers
299 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 ...
user avatar
  • 148k
7 votes
1 answer
155 views

How do they know the sub-surface radar reflections (potential underground ice or "lakes") on Mars are not natural dielectric or metallic in origin?

Gizmodo's NASA Scientists Find More Subsurface Lakes on Mars links to Characteristics of the Basal Interface of the Martian South Polar Layered Deposits (paywalled, but there is this 52nd Lunar and ...
user avatar
  • 148k
3 votes
1 answer
98 views

How were winds measured for ascent trajectory calculations and checks for the Space Shuttle?

The Space Shuttle's ascent trajectory was calculated on the day of launch based on measured winds to avoid structural load exceedances. The winds continued to be measured until shortly before launch ...
user avatar
3 votes
0 answers
192 views

What was the most intense beam ever sent from Earth?

By a freak coincidence sensors on a passing alien ship a hundred light years away had picked up a faint artificial blip from Earth, thereby discovering our inhabited planet. But which blip was it? ...
user avatar
  • 148k
6 votes
1 answer
329 views

How (the heck) was coherent synthetic aperture radar (SAR) implemented using photographic emulsion aboard Apollo 17?

This answer to Is there really microfilm on the Moon? includes a block quote which includes the following subquote: The equipment was installed in the service module and consisted of a coherent ...
user avatar
  • 148k
2 votes
1 answer
210 views

Does Falcon 9's first stage use laser, radar or vision to assist landing? [duplicate]

Does Falcon 9's first stage use only GPS when it makes its vertical precision landing, or is it assisted also by radar or laser ranging or computer vision? If not, why not?
user avatar
  • 26.4k
1 vote
2 answers
285 views

What is "TFR" in the context of operating a marine radar on top of a "water tower" at a launch site?

This answer to What is this propellor-like object on top of the SpaceX Hopper? includes the following: FCC filing: Space Exploration Technologies Corp. 0459-EX-CN-2020: ...d) List any natural ...
user avatar
  • 148k
7 votes
2 answers
342 views

Did the Apollo LM's cockpit altitude displays account for the pointing angle of the radar altimeter?

The Apollo LM had a radar altimeter which was particularly critical in the final stages of landing. It could be set to two different pitch angles, either aimed backwards by 24º to be used during the ...
user avatar
16 votes
1 answer
2k views

Radar altimeter in a space shuttle

I was going through the Space Shuttle Handbook, chapter Guidance and Navigation. In one of the Note boxes, it is written Radar altimeter altitude is not used for navigation or guidance. The ...
user avatar
  • 2,818
8 votes
2 answers
696 views

What are the pros and cons of Doppler radar versus Doppler lidar?

Some spacecraft designed for autonomous landing / hazard avoidance (such as Surveyor) use three-beam Doppler radar for range-rate measurements, and some (such as Morpheus) have utilized a three-beam ...
user avatar
  • 1,070
4 votes
2 answers
204 views

What caused so many objects in Earth orbit to "go NEA"? (no elements availabe)

T. S. Kelso tweeted the following, is this a case of lost and found? How can so many substantial objects become lost like this? The list of 23 objects "formerly known as Prince NEA" all seem ...
user avatar
  • 148k
1 vote
0 answers
60 views

What are currently maximum available radar capabilities i.e. performance/distance for Earth surroundings and deep space?

Afaik I know there is a radar for observing space debris in Germany though I don't know whether it can scan the whole Earth surroundings or just a segment. With respect to asteroids, we discover them ...
user avatar
  • 2,880
3 votes
1 answer
98 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 ...
user avatar
  • 148k
2 votes
1 answer
253 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 ...
user avatar
  • 148k
1 vote
0 answers
45 views

How will the RADARSAT Constellation Mission (RCM) satellites achieve their final orbital spacing?

The informative page shows that the RCM satellites are intended to orbit as follows: Sun-synchronous circular orbit (dawn-dusk mission), nominal altitude = 592.7 km, inclination = 97.74º, period ...
user avatar
4 votes
2 answers
207 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 ...
user avatar
  • 148k
0 votes
1 answer
78 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 ...
user avatar
  • 148k
2 votes
0 answers
179 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 ...
user avatar
  • 148k
4 votes
1 answer
198 views

Why does 2018-099 (SpaceX, December 2018) still have a dozen unidentified payloads?

According to today's Raw SATCAT Data from Celestrak, the launch designated 2018-099 (SpaceX, December 2018) still has twelve unidentified payload objects! ...
user avatar
  • 148k
4 votes
2 answers
542 views

How could a hydrazine and N2O4 cloud (or it's reactants) show up in weather radar?

Question: How could a hydrazine and N2O4 cloud (or it's reactants) show up in weather radar? Tweet: This is what an ‘anomaly’ looks like on weather radar. Tweet (with GIF): Dragon's static fire ...
user avatar
  • 148k
8 votes
2 answers
510 views

How (the heck) do they know some lakes on Titan are 100 meters deep?

JPL News item NASA's Cassini Reveals Surprises with Titan's Lakes NASA's Solar System Dynamics New item Cassini Reveals Surprises with Titan's Lakes point out that some lakes on Titan have been ...
user avatar
  • 148k
3 votes
1 answer
287 views

What is Space Policy Directive 3 and how does it relate to the Space Fence?

In response to a question about the recent ASAT test by India producing a new debris field in LEO, Patrick Murphy, Director of Strategy, Planning, & Integration for NASA Space Technology Mission ...
user avatar
  • 148k
5 votes
1 answer
401 views

What steel ball was thrown out of the ISS to help test how well ground stations can track orbital debris?

The question What kinds of things have been tossed out of the ISS? has a broken YouTube link. This is why it's good to include at least the name of the video in your post (which I didn't back in 2016)....
user avatar
  • 148k
1 vote
1 answer
70 views

Why can Cryosat's dual antenna "better discern steep slopes" of Antarctic ice than Sentinel-3?

The BBC's Climate change: Satellite fix safeguards Antarctic data explains that earlier problems of missing data near the coasts have been addressed, and though scientists are hopeful, there is ...
user avatar
  • 148k
2 votes
1 answer
39 views

What are the trade-offs to use a radio relay orbiter also as a radar science instrument?

Any landed mission could benefit from having an orbiting radio relay satellite to help enhance its data rate to Earth. For polar landers on for example the Moon or Mercury it would be a necessity. For ...
user avatar
  • 180
-2 votes
2 answers
85 views

Space Travel Advanced Recon [closed]

Could a network of probes be sent ahead of a mother ship to form a grid to lay a path for travel inside the solar system? After what certain speed anything larger then a stationary pebble could be ...
user avatar
  • 1
7 votes
1 answer
138 views

How did NORAD notice Kosmos 954 was making erratic manoeuvres?

In Wiki for Kosmos 954 there is: In mid-December North American Aerospace Defense Command, which had assigned the satellite the Satellite Catalog Number 10361, noticed Kosmos 954 making erratic ...
user avatar
1 vote
2 answers
143 views

How could a sextant be used to help in a docking procedure, hypothetically?

If a spacecraft's standard radar and optical metrology were lost, could a sextant be used to determine range and relative position of another spacecraft in order to execute a docking maneuver? Let's ...
user avatar
  • 148k
13 votes
1 answer
1k views

Detailed radar imaging of Tiangong-1; how do they do that?

@JamesPoulose's answer shows an advanced radar image of Tiangong-1, 270 km from the Earth's surface. The images was sourced from Space.com's How Was China's Tiangong-1 Space Station Crash Tracked So ...
user avatar
  • 148k
4 votes
1 answer
195 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 ...
user avatar
  • 148k
12 votes
1 answer
2k views

Why are Titan's lakes "black" in radar images rather than transparent?

Searching after reading Titan rover questions (1, 2, 3) lead me to Space.com's Titan Has More Oil Than Earth which says in part: "Titan is just covered in carbon-bearing material — it's a giant ...
user avatar
  • 148k
3 votes
2 answers
256 views

Number of spectral bands on radar satellites

I have learned that optical earth observing satellites have spectral bands often in groups (e.g. panchromatic, multi-spectral, SWIR, etc.). What about radar satellites such as RADARSAT-1? It seems it ...
user avatar
  • 193
10 votes
1 answer
565 views

Is there really a frozen lake near the equator on Mars?

Figure 1. Views of plate-like terrain on Mars, and pack-ice on Earth. From the paper linked below. a, Part of an HRSC image of Mars from orbit 32, with a resolution of 13.7 m per pixel, centred at ...
user avatar
  • 7,196
10 votes
1 answer
847 views

How does the SpaceBEEs' experimental passive radar reflector work?

My Question: What is the nature of the "experimental passive radar reflector developed by the U.S. Navy’s Space and Naval Warfare Systems Command"? How does it work, and why does it work for ...
user avatar
  • 148k
3 votes
3 answers
818 views

How can ICEYE-X1 capture 2D high resolution SAR images in "tens of seconds"?

The PRNewsWire release First ICEYE-X1 Radar Image from Space Published says: The full image transmitted to the ground from ICEYE-X1 exceeded 1.2GB of raw data and spans an area of roughly 80 x 40 ...
user avatar
  • 148k
6 votes
1 answer
645 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 ...
user avatar
  • 148k
3 votes
1 answer
488 views

Why are there so many waveguide feeds (?) near the focus of Cassini's dish antenna?

Cassini has quite a complex Radio Science Subsystem. Accorting to that article (and confirmed in Wikipedia): Cassini is the only deep space mission to transmit to Earth at three radio wavelengths (...
user avatar
  • 148k
0 votes
1 answer
51 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 ...
user avatar
  • 148k
10 votes
1 answer
966 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,...
user avatar
  • 148k
6 votes
1 answer
441 views

How many antennas does Kurs use in toto, and what are each of their functions?

I learned about the Kurs docking system in this answer, then found out what they looked like in this and in this answer. Those images show several tiny dish antenna structures sticking out from ...
user avatar
  • 148k
2 votes
2 answers
816 views

Parallel orbits around the Earth - effectively?

edit: For the purposes of this exercise, one could consider using three or four identical spacecraft, and using the "best two out of three (or four)" for interferometry at any given moment. In 1994, ...
user avatar
  • 148k
4 votes
1 answer
439 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 ...
user avatar
  • 148k
12 votes
4 answers
770 views

Why was the 100m Green Bank dish needed together with DSN's 70m Goldstone dish to detect Chandrayaan-1 in lunar orbit?

The Phys.org article New NASA radar technique finds lost lunar spacecraft describes the use of radar to relocate two spacecraft that were in orbit around the moon but who's orbit had not been actively ...
user avatar
  • 148k
2 votes
1 answer
171 views

How can ISRO's RISAT satellites search for the lost IAF AN-32?

The Indian Air Force has lost contact with AN-32 (transport aircraft) on a mission. ISRO is going to deploy RISAT to search for the missing plane as the search area has widened. How will such ...
user avatar
  • 569
1 vote
1 answer
128 views

Fielding Photonic radar in outer space

A new type of radar. How will photonic radar behave in outer space? What will be challenges faced by such radar ? How will it differ from pesa on Soyuz-MS ? Will such radar be termed as space weapon ...
user avatar
  • 569
8 votes
2 answers
1k views

What is the current record for the farthest detection of a "dead" spacecraft?

In order to better defend my position that trying to track Juno from Earth once it can no longer transmit would be Quixotic, I'd like to ask what the current record is for the farthest detection from ...
user avatar
  • 148k
9 votes
2 answers
782 views

Is this the longest that a spacecraft "went to sleep" and then woke up on schedule?

For various reasons, spacecraft are sometimes "put to sleep" for periods of time on long voyages. Many systems are shut down, and radio communications suspended. Tracking of spacecraft at very large ...
user avatar
  • 148k