We use the Celestial Altium Library [1], it's really good for passive components, which make up ~80% of our schematics by count. For other parts we first try to get them through Altium Manufacturer Part Search, we vet the symbol and footprints before importing them into our internal library. Other model sources in order of preference is SnapMagic, UltraLibrarian, Samacsys. Be aware as the quality is often half-baked. Between components that meet my requirements, I will always pick the one with CAD models easily available.
With those prerequisites I only have to make 2-3 footprints from scratch per project as needed, and less so as our library grows.
The Proba missions are technology demonstrators. The main goal of Proba-3 is to demonstrate precision formation flying [1], which would enable large instruments in space without the need for large mechanical structures and complicated deployment mechanisms. Even in the age of Starship this could be useful.
The coronagraph is one example of an instrument that benefits from formation flying, but its actually considered a guest payload on Proba-3. Benefits of formation flying include being able to adjust the distance between the two spacecraft to block more or less of the Sun disk. Also in traditional coronagraphs the occluding disk is held in place with struts that obscure parts of the corona.
Other applications that could benefit are telescopes (radio, optical, X-ray), interferometric SAR, in-space inspection and servicing of existing satellites, to name a few.
Commercial Crew is fixed-price contracts, whereas cost-plus contracts has been the norm in the US aerospace industry. Boeing is the one bleeding money here.
Like I said, it doesn't cost them much. It's not zero cost - people have to talk to Boeing, yell at them when things are broken, review fixes and proposals, etc.
You should look up image sensor dark noise. One way to reduce dark noise is taking an exposure without any light on the sensor, it should give you the fixed pattern which can be subtracted from your scene image. Dark noise is sensitive to temperature and exposure time, so you should try to do this under similar conditions.
I implemented it just now. Turns out when performing the subtraction on the raw data before applying the color space conversion LUT, it's also necessary to add the mean of the noise image's pixel values because otherwise some bias is lost and the entire image's brightness changes. With this in place, it seems to work. Interestingly enough, this even results in noticeable noise reduction when the noise image was not recorded in the same environment but only with the same camera settings!
When performing the subtraction after applying the LUT (that is, result = apply_lut(raw) - apply_lut(raw_noise) instead of result = apply_lut(raw - raw_noise + mean(raw_noise))), the result is quite different for reasons that I don't fully understand yet, but the noise is reduced in the same way. This will need some further investigation.
Ancient? The HF band is still very much in use... Modern developments have not changed the fundamental properties of RF propagation. UHF ("a few GHz") can only be propagated in line of sight reliably. HF can literally travel around the world.
GP called the term ancient, not the band itself, and I find it hard to disagree with that.
Calling something “high”, “fast”, or “new” is rarely a naming decision that’ll stand the test of time, but given that there were already LF and MF below it, it did make sense at the time. Who could have predicted we’d go up all the way into visible light with our RF communications?
The only thing on a lower frequency used daily by most people would be contactless payment cards and maybe NFC at around 13 MHz.
Millimeter wavelength RF was already studied in the 19th century... The RF communication band you're talking about is smack dab in a band already defined in the original 1937 document.
Honestly the naming scheme makes sense to me. The spectrum is divided into 12 bands of equal (log) size, up to a frequency where we don't know whether such waves will ever be reliably generated at room temperature without breaking the laws of physics. Then these bands are consistently named from "extremely low" to "extremely high", with an extra annoying band at the top. Really, it could be worse.
I agree it could be worse but the idea it's really any good seems more like us being used to it than anything else. It's a stupid naming scheme. For a log scale I would really have been happier with everyone using band numbers or something rather than explaining "super high frequency" is higher than "Ultra high frequency" and, despite the terms, that's probably where most typical radio device use cases are these days.
Fortunately we have not just one but two competing band designators – IEEE (widely in use in e.g. satellite communication; L-band, Ku-band, Ka-band etc. come from that nomenclature) and EU/NATO (which seems somewhat obsolete) :)
In addition to that, hams (in study materials and exams) use wavelengths, which is always "fun" to convert from/to frequencies.
I'm not sure I understand. In 1937 we already knew that light and RF are both part of the EM spectrum so I don't know what you mean by generating waves that break the laws of physics (we have and had absolutely no issues generating waves with 100s of THz frequency). As a physicist coming from the optics I find naming in RF often quite puzzling, e.g. why do we call it microwave, while wavelengths are all longer that millimeters?
> we have and had absolutely no issues generating waves with 100s of THz frequency
In a way suitable for even medium range RF communication? No. That's what I mean. The required power would be insanely high. So high that it's not achievable without some breakthrough. I didn't literally mean "break the laws of physics", because that's something we obviously cannot do.
What do you mean? We routinely do satellite communications with free space optics, and fibre comms which at the backbone of all modern comms uses light around 193 THz.
UHF can be used with troposcatter techniques. Before satellites this was somewhat popular. It seems to be having a little bit of a comeback as well as you can get hundreds of miles of propagation fairly reliably and since it's higher frequency you can get a pretty wide bandwidth. Something that can fit on a small trailer can send hundreds of megabits hundreds of miles.
I mean, any higher and I’ll have to start thinking about printed circuit boards, shielded wires, and non-coat-hanger-based antennas…frankly if 30,000 kilocycles can’t get the job done, I’ll just have to light the thing on fire and use it to make smoke signals.
Laplace and z-transform are widely used in control systems and signal processing. Both are more general forms of the Fourier transform in continuous and discrete time, respectively.
