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 ...


9

The material depended on the mission but was usually quartz, and the stability is insane. The development of Ultra-Stable Oscillators (USOs) is ongoing (see here and here). NASA/the ESA have used things like quartz and rubidium depending on the mission (see the abstract) . Crystal oscillators are preferred because they are "...easier to qualify for deep ...


7

NOTE: This discusses autonomous car sensors but the same physics will apply to any longwave vs. shortwave sensor comparison (cost being the wildcard) An interesting parallel is Tesla Inc.'s decision to use radar as the active component for their autonomous driving system rather than (much more common) LIDAR. My recollection of the costs/benefits of radar ...


6

"Weak capture" means that the spacecraft will enter the Mercury's gravitational sphere of influence along a weak stability boundary. These weak stability boundaries are one of the key mathematical developments of the N-body (N>2) with regard to space exploration. The entry points to this weak capture are rather narrow, in terms of both position and velocity....


5

From your link: If the orbit had been perfectly circular at the 128.2 minute period the doppler shift for a simple transmitter would have been = 2287.5 x 1000 x 1.58/300000= ± 12 kHz. For a coherent transponder the doppler shift would be almost double this number (doppler shift on both uplink and downlink), i.e. 46 kHz.


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 ...


4

If you look at the "more detail" section of the DSN status web page, you'll see that 25 and 26 are operating in "array mode". With two antennas receiving, twice as much incoming signal is being caught, and because the dishes are physically separated, some local noise sources will appear in one receiver and not the other, making it easier to discriminate ...


4

From the NASA Space Science Data Coordinated Archive entry on Hagoromo, The ignition of the Hagoromo deceleration rocket was confirmed by ground observation at 20:04:03 UT. From a few other sites, this was done at the Kiso Observatory in Japan using a 105 cm Schmidt camera. The satellite would have been ~22 magnitude and near the Moon, so hard to see -- ...


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

Yes, and yes. The standard Doppler data type on deep-space spacecraft is X-band to X-band, and transmit and receive are on the same antenna. Most deep-space spacecraft only have X-band transceivers. A few have more than one band, usually for either radio science reasons and/or higher data rate on Ka (accepting some added risk of weather interference). S-band ...


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 ...


2

I think you mean to ask the question about LIDAR as used for velocity measurement in spacecraft rather than the LIDAR used in autonomous vehicle. Here, I list some few points relating to both altimeters and velocimeters both. Ka-Band Radars/Velocimetry It has advantage that, one can actually get sort of averaged information about altitude and velocity ...


2

32 meter antenna of IDSN is being used by JAXA and ISRO to study Venusian atmosphere using signals from Akatsuki probe and Radio occultation technique. ISRO is also planning a Venus mission so these results are of mutual interest. Excerpt from Annual Report 2016-17 of Dept. of Space (India) The space agencies of India and Japan have agreed to further ...


2

Since the deep space network can perform ranging on spacecraft much farther away (tens of thousands of times farther than the moon) by itself, why was it necessary to use a non-colocated, non-DSN dish to receive signals in this case? The ranging you're referring to is cooperative radio ranging: The DSN sends a signal to the spacecraft, the spacecraft ...


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