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The Apollo Guidance Computer used a state vector either centered at the Earth or the Moon. The switchover point is the the lunar sphere of influence, defined in the AGC as 64,373,760 meters (https://www.ibiblio.org/apollo/NARA-SW/R-577-sec5-rev4-5.6-end.pdf PDF page 127). When in the idle program P00 the AGC will periodically check if it needs to update the ...


29

Why not? Because we can't. We don't have full-time communication with Curiosity: Curiosity sends data to the Mars Reconnaisance Orbiter and Mars Odyssey. These are overhead twice a day at 12-hour intervals. MRO and MO are in sun-synchronous orbits, so the planet rotates underneath the orbiter and they cover the entire planet in 1 day. Both are in orbits ...


25

First you lock on to energy at (or near) the expected frequency. That’s carrier lock. Then you start to look for patterns in how the phase changes. The transmitter is coding groups of bits as phase-change “symbols”, and you want to find the time-pattern of those: symbol lock. But those are not yet bits because the coding works in blocks of bits. Once you ...


16

The live broadcasts from the Moon were not recorded on the LEM/CM. Video tape recorders were too large at the time to make this practical. They usually came in the shape of an open-reel tape recorder with 2" wide tape. This is the Ampex VR-660, a "portable" VTR that weighed 50 kg: NASA used the VR-660 at ground stations to store slow-scan video. The ...


9

"We should wait for all the problems on earth to be solved before going into space". I've seen this sentiment multiple times, and I disagree vehemently. 1. There are other much more worthy targets of this kind of argument Whenever a space mission has cost overruns in the billions, I convert the dollar amount into B-2 bomber equivalents. That is, 2 billion ...


9

Two items of note: Luna 9's initially released pictures came from scientists at Jodrell Bank Observatory in England, which could be received because they were in a standard format. This came ahead of the official release of the first photographs from the surface of the Moon. Apollo 11 signals were received and decoded by Amateur Radio operators. Many ...


9

Vacuum would have a $\tau$ of zero. An opacity of $\tau$ means that the atmosphere is reducing the direct intensity of light from the Sun, if it were directly overhead, by a factor of $e^{-\tau}$. It was measured by the rovers every sol by pointing the PanCam at the Sun, or where the Sun is supposed to be, measuring the intensity, correcting for the slant ...


7

You have to remember that technology was much less advanced at the time of Sputnik 1. It’s ability to downlink information was tiny, and the science was organized around that: The ball was pressurized, and the skin and internal temperatures were (the only?) quantities downlinked. This was used to put a lower limit on micrometeoroid impact rate, as a leak ...


7

Hobbes' answer is correct, but here is some supplemental information. The Erectable S-Band Antenna was a parabolic dish that was folded and stowed in the descent stage. Page 4-86 of the Apollo Program Summary Report describes the diameter as 10 feet and this NASA webpage says 3 meters. It was carried on Apollo 11-14. Although the LM could broadcast with ...


7

note: Here are two examples of "hijacked signals" that include "public release of the images or data that included the admission that it is 'stolen' or 'hijacked'." I am sure there are a few more. One is backyard audio and the other is intercepted video! From Lunar Eavesdropping in Louisville, Kentucky by C. Graney, Jefferson Community & Technical ...


6

Signals are not repeated, but instead coded in a special way that allows to reconstruct the original data on the receiver side in presence of noise/errors. It is called forward error correction. FEC schemes are more efficient than just blindly transmitting the same data twice (though they of course increase the total amount of data that has to be ...


6

Communications, and the data rates available, boil down to signal-to-noise ratio (SNR): the power of the signal within a receiver's bandwidth divided by the noise power the receiver sees in that bandwidth. This is true regardless of whether the receiver is electromagnetic (radio, laser comm, etc.) or acoustic. Once you get an SNR higher than the threshold ...


4

The Parker Solar Probe keeps its heat shield towards the sun at all times, even at aphelion: Source: NASA/JPL During part of the cruise/downlink portion of the first pass, the heat shield is pointed near Earth: Source: Here's the orbit NASA's Parker Solar Probe will take around the sun, Science News (Youtube) But the HGA (High Gain Antenna) used to ...


3

It's generally true that the error rate in communication is proportional to the energy per bit. Rigorously you can see this through things like $E_b/N_0$ and the Shannon Hartley theorem. To compensate for the greater distance to Mars, one could either increase the transmitter power or antenna gain to maintain the same power, or transmit each bit for a longer ...


3

Those people in the control room just see various things on their screens (see the attached image). It is quite evident that not all the monitors show the same data. NASA JPL Mission Control Room, shortly after a woman said "Touchdown confirmed." Watch this video, especially after minute 53. However, it is a bit baffling that immediately, seconds after the ...


3

Just a single repetition would not help. If there is a single error within those two data blocks, you do not know where the error is and have no chance to correct the error. If the data is transmitted three times and you get two identical copies, you may assume those identical copies are correct and one or more errors are in the third block. A better ...


3

"We shouldn't spend any money on [insert item of your choice here] until we have solved [insert interest that is dear to your heart here]." In practice, that means we would never spend money on the venture because we can safely assume that the problem that must be solved first will never actually be solved. Anything that is not the problem that needs to be ...


3

It's not impossible: The Pioneers have not been switched off (as evidenced by the later successful attempts to contact them). They're in constant sunlight so no thermal cycling which increases their life expectancy, and no batteries are necessary. There has been at least 1 other case where an old spacecraft was found to be alive after years of no contact (...


2

The video and audio were not packaged in the same file: InSight did not produce a video file with audio tracks. As you can see in the screenshot, the 'audio' was recorded by the seismometer instrument (SEIS) as vibration data. This can be converted to audio (after all, audio is also vibration data), but this was done after reception. NASA did some ...


2

What could be the complete internal architecture of my payload's OBDH system? I would use a Raspberry Pi model 3b+, connected to a camera module. You may run the latest version of Raspbian (a Linux flavor based on Debian) and configure the startup scripts to start streaming footage. Which processor should I use for fast processing, less power budget? ...


2

A lot more of this has to do with the physical nature of the cable than the signal protocol, in that you get the best cable you can and then adjust your signalling method to move as much data as physics will allow. The classic solution for 1km distances is RS422 though various alternatives exist, including all those intended for two wire telephone use that ...


2

Governments do lots of things despite the existence of poverty. Investment in all kinds of science, in the military, in infrastructure, etc. all proceed despite poverty. And this is a good thing. If governments limited themselves to fighting poverty, they might eradicate poverty but we'd be stuck in the 1940s technology-wise. Computers, the internet, modern ...


2

Your question has 2 main points: Can satellites record video? Both Pleaides and Skysat have the capability to record videos. Can satellites downlink real-time payload data at the required throughput for video? AFAIK, Skybox requires pointing to its ground station, while I suspect Pleiades does not need to do so. Theoretically then (and up to SW ...


2

Here is one example (this is ESA actually), I am sure there will be others posted. This is a 2D histogram for the ExoMars Schiaparelli Lander, Schiaparelli’s UHF Signal captured by GMRT prior to Entry – Photo: ESA Data was received from the Giant Metre Wave Telescope in India. See Was the time of Schiaparelli's landing chosen specifically so the Giant Meter ...


2

The instrument is described in the Apollo 16 Preliminary Science Report document as "the far UV camera / spectrograph". The whole of Chapter 13 of this document is dedicated to a description of the instrument, its use during the mission, and preliminary results from it. I am having difficulty copying text out of the pdf, so here is the page with the ...


2

Tracking Apollo-17 from Florida http://www.svengrahn.pp.se/trackind/Apollo17/APOLLO17.htm On December 10, 1972 we picked up our first signals on S-band. The main carrier was 45 dB over noise and the voice subcarrier was 25 dB over noise. Apollo 17 passed. over the lunar disc between 1722 and 1819.10 local time (2222-2319 UT), and during these 57 minutes ...


2

https://www.roscosmos.ru/24173/ The main tasks of the satellite were: verification of calculations and basic technical decisions made for launch; ionospheric studies of the passage of radio waves emitted by satellite transmitters; experimental determination of the density of the upper layers of the atmosphere by deceleration of the satellite and ...


1

The messages being displayed on the console are NMEA, a plain ASCII text format (not hexadecimal). To do anything further with them you'll either need to write software yourself to interpret it or use 3rd-party software to do so. I've done both myself in both Perl and C++ and it was very simple and straightforward to do (here is a random example of doing ...


1

The receiver will likely use a filter matched to the 160 cps bit rate. This will reduce the transmit power in 1KHz BW by about 7.95 dB. The filter will however have a 1 to 2 dB mismatch loss. If this mismatch loss is 1 dB then the SNR =3dB+7.95dB-1dB=9.95 dB based on the initial SNR derivation.


1

For short videos of Earth this can be done with surprisingly nice results from low Earth orbit (LEO) with a little image processing to flatten and align the image and generate the appearance that the spacecraft is hovering. These videos are only about 15 or 20 seconds and you can't choose a place and time arbitrarily, so I don't think this technique offers ...


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