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14

It was done with one single dish, ...in Ku-band (16.7 GHz) and ... currently equipped with a high target resolution. The Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR)'s March 21, 2018 press release - the original source of the picture in the question - links to an introductory description of their Space observation radar TIRA ...


13

This article suggests that the radar can penetrate the lakes and reports them to be hundreds of meters deep. The space.com article referenced seems to be sourced from a Geophysical Research Letters article from 2008 (not paywalled) which gives the radar wavelength (2.2cm) and claims that it would be absorbed in 2-20m of clean hydrocarbon, but also give other ...


12

There are two potential candidates that I'm aware of. The first is J002E3, which is believed to be the Apollo 14 Saturn 5 upper stage. At the time of detection, it was orbiting Earth between 1-2 lunar distances away. Another candidate is 2007 VN84, also known as Rosetta, which was discovered via an optical survey while Rosetta was on a close approach path ...


10

OK, here's the Link from NASA. Spacecraft velocity is determined by measuring the Doppler shift of a coherent downlink to determine its earth-relative velocity. Spacecraft distance is measured by sending a uniquely coded ranging pulse to the spacecraft (including the transmission time of the pulse) and then measuring the time it takes for the spacecraft to ...


8

This paper reports SHARAD observations of this site, and also references previous publications based on an earlier radar instrument MARSIS. It's complicated and the data seems to be ambiguous, but the bottom line appears to be that it isn't a large lake of solid ice. It might be broken up volcanic rock with ice filling the spaces, or it might just be rock. ...


8

What are radar calibration spheres I couldn't find any specific information about the SKRL calibration spheres, but based on descriptions (passive, spherical satellites) and information about other radar calibration satellites (LCS) I'd agree with your guess that they're simply hollow metal targets. Radar calibration requires known data to compare with the ...


7

Many questions! How effective are different types of radar in space over large distances. Is radar significantly different outside of the atmosphere of Earth? The only difference between a radar inside the atmosphere and in space is the lack of air to dim the signal. Instead, a usually small angular size of the target, caused by the large distances. ...


7

I might go look for some links, but just off hand Doppler velocity is good to less than 1 mm/s (in the line-of-sight dimension), can be as good as 0.1 mm/s, ranging is good to better than a meter (also in line-of-sight), and delta-DOR position in one dimension, in the plane connecting the two DSN complexes and the spacecraft, is good to about 1 nanoradian. ...


7

The paper itself (I have access) says and shows that they are detecting the bottom of some lakes with their radar with a maximum depth of 105+/-6 meters. The radar reflection off the bottom is much fainter than off the surface, but still distinct and clear. The attenuation (17 dB/us) fits a mostly-methane composition (best fit 69% methane, the rest mostly ...


7

From Cassini observations the methane-ethane mixture (with methane by far the largest component, maybe with some dissolved nitrogen) appears so pure that its absorptivity at the RADAR instrument's Ka-band frequency is quite low. That's how it could see so deep — not just 100 m, but 160-170 m. The paper The Bathymetry of a Titan Sea by Marco Mastrogiuseppe ...


7

Hydrazine has a lot of spectral structure in the microwave regions (see paper), as does dinitrogen tetroxide (sorry, only paper I have is paper). This means that they’re pretty good at absorbing and reemitting, hence reflecting, microwave radar energy. Reflections are what the radar displays Off hand, hydrazine has such a thicket of strong lines that it’s ...


6

The original 4 satellites were 0.25U cubesats (as shown in the picture in the question) while the newer ones are 1U (cubical). The larger size of the newer sats provides space for Van Atta reflectors on four of the cube's faces1. Here's my understanding2 of how the reflectors work: In their most basic form, Van Atta reflectors are fully passive phased-...


6

Surveyor measured the rate of descent with radar by using Doppler shift. From the book Planetary Landers and Entry Probes: The surveyor lander used a pulsed radar to generate an altitude reference at 100 km, a separate RADVS (Radar Altimeter and Doppler Velocity Sensor) turned on, using a four beam frequency modulated continuous wave technique (Figure 5....


6

First of all, yes, Rosetta was indeed without any contact for 31 months. That is longer than New Horizons, which wasn't in hibernation for more than 202 days. These are the only two spacecraft that I can find that meet this criteria.


6

These maps were produced with doppler-delay imaging, which uses a combination of range and motion to identify the radar return from each specific point on the surface and build a map. Longitude is determined from doppler shift - as Venus rotates, one side of the planet is moving towards Earth while the other is moving away. Latitude is calculated from the ...


5

The explanation has to do with the operation of the radar transmitters and the round trip light travel time. It takes about 3 seconds for a radar pulse to travel from the Earth to the Moon and back. The planetary radar transmitters are high power; the Goldstone transmitter (at full strength) is 500 kW, the Arecibo transmitter is nearly 1000 kW. By ...


5

Within the solar system you cannot really travel 'ahead' of a transfer orbit since it would have required you to have departed from a point in space ahead of the origin body (for example Earth) in it's solar orbit. It would be possible to fly approximate trajectories but they would be more costly in fuel. Bigger problem is that they will only warn of ...


5

Weather radar is not specifically measuring clouds or water in the atmosphere. What is measured is the amount of microwaves in the 5 GHz range reflected by anything in the atmosphere. This can be water droplets, but as well be insects, birds or any other kind of droplets, like propellant that didn't stay where is was supposed to be.


4

The basic problem with using radar in space is range. When you send out a radar pulse, the amount of power that returns to the transmitter is proportional to 1/range4. So double the distance means power drops to 1/16. On Earth, that's not a big problem. To detect objects in the atmosphere (e.g. aircraft), you can build a transmitter powerful enough to ...


4

I see different versions of Cyrillic transliterations in my sources; I have chosen consistency. There are 6 Kurs antennae. For some reason NASA labeled two of them with the single number "3". Refer to the images for antenna location (yellow numbers on the graphic, red numbers in the photo): The descriptions come straight out of the linked paper. They ...


4

Some of those are the Ku-band antenna feeds for the Radar. The high-gain antenna also serves (served) as part of the Radar science instrument. The HGA was pointed at Titan many times to get synthetic-aperture radar images of the surface of Titan, otherwise obscured by the haze in the atmosphere to visible light instruments.


4

Broadly speaking, SPD-3 establishes new roles and responsibilities for SSA (Space Situational Awareness) and STM (Space Traffic Management). It shifts the responsibility of managing SSA data (which includes object tracking and collision warning issuance) from the Department of Defense to the Department of Commerce. This shift of responsibility to a civil ...


3

Absolutely ! To be able to perform a rendez vous, you need to know your current position, heading, orientation, and velocity, as well as that of the target craft. 2D Coordinates: The sextant can give the first information, provided the altitude (dip) is known. 3D Coordinates: The altitude could be extrapolated from an angular measurement of the horizon of ...


3

Full disclosure: ICEYE employee, I'll try my best to answer. Thank you for asking and being interested in ICEYE-X1! The "amount of seconds" refers to the amount of time the satellite is actively imaging data for an individual frame. I would not recommend referring to the current Spaceflight101.com article for technical specifications on ICEYE-X1. The ...


3

ICEYE-X1 does not have a vertically large antenna, so it can only provide 2D data. To interpret the image correctly, you can imagine the satellite crossing over the top of the image from left to right, looking sideways. The axis are: x-axis: position along track y-axis: slant range color axis: reflectivity None of these measurements requires a large ...


3

A few issues with what you included: The resolution is stated as 10m in the bit you included. The size of the image was 80 km/ 40 km The frequency is 10 GHz, meaning a wavelength of about 3 cm. The SAR antenna is deployable, meaning the effective beam width can be greater then the satellite. Of course, the total width is about 3.2 m, as you indicated. The ...


3

Three-way Doppler tracking was developed for when the spacecraft (specifically Voyager) is so danged far away, that by the time the round trip signal gets back to Earth the original transmitting complex has rotated out of view. Then the signal is being received at a different complex. Then there needs to be a third link between the two complexes for a phase ...


3

I know nothing of the activity you're asking about, but I do know something about radar. All the radar systems I've worked with used a single antenna to both transmit and receive. The power of the transmitter is very large compared to the return echo that needs to be received, and the very sensitive receiver needs to be disconnected from the antenna when ...


3

The use of a sextant by itself isn't the limitation, it's having to do calculations by hand instead of by a computer. I agree with uhoh's comment that the final approach can be done manually, without either the computer or the sextant. For example, the extraction of the Apollo lunar module from the 3rd stage could easily be done manually. I saw an article ...


3

NORAD uses radar to track the position of satellites. When you observe a satellite a few times, you can calculate its orbit and predict where the satellite will be in the future. When a satellite manoeuvres, it changes its orbit so it won't be at the predicted position. If your tracking system is good enough (=you need frequent observations), you can see ...


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