UmbralRaptor changed the topic of #kspacademia to: https://gist.github.com/pdn4kd/164b9b85435d87afbec0c3a7e69d3e6d | Dogs are cats. Spiders are cat interferometers. | Космизм сегодня! | Document well, for tomorrow you may get mauled by a ネコバス. | <UmbralRaptor> egg|nomz|egg: generally if your eyes are dewing over, that's not the weather. | <ferram4> I shall beat my problems to death with an engineer. | We can haz pdf
<raptop> !choose eat|eat
<galois> raptop: Your options: eat, eat. My choice: eat
<raptop> eggcelent choice
<egg|anbo|egg> raptop: KerbalismContract question: how does one prevent a handful of KH-11s essentially winning the remote sensing game (i.e., is their imaging limited by some sort of exposure/pointing considerations)?
<egg|anbo|egg> I guess the limitation is just the smol swath and then the fact that pointing time is still much smaller than the motion across the sky (no spinning a KH-11 like it’s an MSG SEVIRI to get infinite swath) ?
<raptop> smol swath, there was an era when they couldn't do much of pointing, and they sometimes have time-sensitivity
<egg|anbo|egg> three KHes earlier but per millimeter at a 2:1 image contrast and an overall optical figure of 1/10)". GAMBIT was to carry 3,000 feet of 9.5-inch-wide, thin-base film through a strip camera, which would provide image-motion compensation by moving the film across an exposure slit at the same velocity that the projected image moved over the earth. When looking vertically, the camera would image a strip on the earth 10.6
<raptop> Also, doesn't the US currently only have like 4 KH-11 equivalents up?
<egg|anbo|egg> ah that got cut off: When looking vertically, the camera would image a strip on the earth 10.6 nm wide.
<egg|anbo|egg> I am going to assume those are nmi, not nm
<egg|anbo|egg> otherwise this is a very smol swath
<egg|anbo|egg> raptop: yeah, but even if they had a dozen that wouldn’t put a dent in the need for weather sats and the like so I am trying to figure out how to model that
<egg|anbo|egg> if you don’t model pointing and the satellite can magically spin around to look at all the things, it gets silly :-p
<egg|anbo|egg> nominal exposure time for the GAMBIT-3 strip camera is 6.72 ms
<egg|anbo|egg> (but they have this scrolling film trick so it’s not as blurrycam as that would imply, they mention 6 ft)
<raptop> >6 ft
<raptop> socially distanced satellite
<egg|anbo|egg> please stand far enough apart that GAMBIT-3 can resolve you
<raptop> :D
<raptop> I mean, FoV is a big thing here
<raptop> Also to some degree wavelengths (compare visible for spy sats vs IR for clouds vs radiometers for ice)
<egg|anbo|egg> yeah FoV is the obvious difference, but spy sats do pointing far from the nadir so you can’t just treat it as tiny swaths (otherwise you would never see anything in time with your poor KH-11)
<egg|anbo|egg> so then the question is how to model it so it doesn’t do all the things by instapointing to anything you want to see that is above its horizon
<egg|anbo|egg> do they track points on the surface or just shift their swath cross-track
<egg|anbo|egg> the last image on https://what-if.xkcd.com/32/ makes the former hypothesis but it seems there’s a lot of talk of swath at least in the earlier KH docs
<galois> title: Hubble
<galois> Pillar | Alt-text: A comic by my brother Doug, redrawn and rewritten by me
<raptop> Unsure, though I do no that they did minor orbit adjustments for getting better images or images at better times (past tense because the interviews were for vietnam era intel)
<raptop> Uh, the war vietnam fought with the US, not the one with Japan, the one with France, the one with China, the one with Cambodia, or the other one with China
<egg|anbo|egg> yes, the American war
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<raptop> ...random thing from poking wikipedia: ceres may have marginally lower surface gravity than charon
<raptop> !choose chronic illness|cthonic illness
<galois> raptop: Your options: chronic illness, cthonic illness. My choice: chronic illness
<egg|cell|egg> ... if we assume that KH-11 is WFC3 pointing down that's an FoV of 230 m? That seems too smol
<raptop> I suspect that WFC wants to be diffraction limited at 200 nm for UV porpoises?
<raptop> *WFC3
<raptop> Naively apply 10 cm/pix, 1200x643 becomes 120x64.3 m (the smaller number of course wrong because of the angle)
<raptop> !acr -add:LIFE Large Interferometer For Exoplanets
<galois> Definition added!
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<egg|laptop|egg> !acr -add:Alcatel ALsacienne de Constructions Atomiques, de TÉLécommunications et d’électronique
<galois> Definition added!
<egg|laptop|egg> whitequark: TIL
<whitequark> de constructions what
<whitequark> ohhhh that would explain a lot actually
<egg|laptop|egg> atomic! https://fr.wikipedia.org/wiki/Alcatel#Alcatel_et_CGE,_deux_entreprises_diff%C3%A9rentes
<galois> [WIKIPEDIA] Alcatel#Alcatel et CGE, deux entreprises différentes | "Alcatel (acronyme d'Alsacienne de constructions atomiques, de télécommunications et d’électronique) était une entreprise française spécialisée dans le secteur des télécommunications. Elle fusionne avec Lucent Technologies au mois de décembre 2006 pour devenir « Alcatel-Lucent ». Alcatel-Lucent est rachetée…"
<egg|laptop|egg> uh, why did I link to that subsection
<egg|laptop|egg> ah here is the relevant merger https://fr.wikipedia.org/wiki/Alcatel#Soci%C3%A9t%C3%A9_alsacienne_de_constructions_m%C3%A9caniques
<galois> [WIKIPEDIA] Alcatel#Société alsacienne de constructions mécaniques | "Alcatel (acronyme d'Alsacienne de constructions atomiques, de télécommunications et d’électronique) était une entreprise française spécialisée dans le secteur des télécommunications. Elle fusionne avec Lucent Technologies au mois de décembre 2006 pour devenir « Alcatel-Lucent ». Alcatel-Lucent est rachetée…"
<egg|laptop|egg> En 1963, sont regroupées sur site du Château Rouge la Société Alsacienne d'Electronique et de Mécanique Appliquée (SAEMA, filiale de la SACM), le département ENTE9 et la SOLMEA pour constituer la Société Alsacienne de Constructions Atomiques et de Télécommunications (ALCATEL)
<egg|laptop|egg> where ENTE is ENTE (Energie Nucléaire, Télécommunications, Electronique)
<egg|laptop|egg> !acr -add:SACM Société Alsacienne de Constructions Mécaniques
<galois> Definition added!
<egg|laptop|egg> !acr -add:ENTE Énergie Nucléaire, Télécommunications, Électronique
<galois> Definition added!
<egg|laptop|egg> note: it also means duck in German, which may well be intentional given that it’s an alsatian company
<egg|laptop|egg> !acr -add:SOLMEA SOciété Lilloise de Mécanique et d’Électronique Appliquée
<galois> Definition added!
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<raptop> !acr -add:ORC Odd Radio Circle
<galois> Definition added!
<raptop> !wpn
* galois gives raptop a red reference with a disc attachment
* raptop stabs sleep with a red reference with a disc attachment
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<egg|anbo|egg> Hm, LRO NACs have a swath of 5 km
<egg|anbo|egg> EROS?
<egg|anbo|egg> !acr -add:EROS Earth Resources Observation Satellite
<galois> Definition added!
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<raptop> Well that went surprisingly well
* raptop means the QM qual. I don't follow inagurations
<WeylandsWings> Was this your last qual
<WeylandsWings> Also why in the world was it scheduled on Inauguration Day
<raptop> I think the pandemic pushed everything (quals, start of classes) back a week
<raptop> And hopefully it was my last
<egg|cell|egg> Neo Assyrian too
<egg|anbo|egg> looks like that says 𒊩𒄀
<galois> title: rinap/rinap3/akk/šalgu[snow]
<raptop> yay, snow
<raptop> company name idea: iridium heavy industries
<raptop> (osmium, etc also work)
<raptop> !choose byzantine fault tolerance|turkey's seismic construction code(s)
<galois> raptop: Your options: byzantine fault tolerance, turkey's seismic construction code(s). My choice: byzantine fault tolerance
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<raptop> " Due to system conversion, the Job Detail will display an Effective Date of July 1, 2002."
* raptop ???
<WeylandsWings> raptop: say only if you get paid from that date
<raptop> hah
<egg|anbo|egg> hm, the diffraction limit for VIIRS I1 would be 3 m at the diffraction limit, rather than the actual 375 m, so I guess I have to take other factors into account >_>
* raptop has a silly thought
<raptop> It's going to be amusing if the 2022 form 1040 has a deduction for getting a COVID-19 vaccine that was not covered by insurance
<egg|anbo|egg> raptop: what limits the resolution on a thing like VIIRS?
* raptop isn't familiar with the instrument, though I assume the wide spectral range limits some things in the design
<raptop> hm, it's 19 cm in diameter
<raptop> Also the talk about swathes makes it sound like a pushbroom o_O
<egg|anbo|egg> yeah it has a rotating telescope
<raptop> hrm, speed/altitude and exposure time would limit things
<egg|anbo|egg> but they don’t limit things anywhere that much for most imaging satellites
<egg|anbo|egg> !acr -add:AVHRR Advanced Very-High-Resolution Radiometer
<galois> Definition added!
<egg|anbo|egg> it’s radiometry, not sure what that implies
<egg|anbo|egg> at 12.4 μm the diffraction limit would be 65 m so the I5 band is closer to that, but it’s weird that the visible imaging bands are so far from the diffraction limit O_o
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<egg|laptop|egg> same story on MSI, the band with the shortest wavelength has the lowest resolution?!?! https://fr.wikipedia.org/wiki/Sentinel-2#Instrument_MSI
<galois> [WIKIPEDIA] Sentinel-2#Instrument MSI | "Sentinel-2 est une série de satellites d'observation de la Terre de l'Agence spatiale européenne développée dans le cadre du programme Copernicus dont les deux premiers exemplaires ont été mis en orbite en 2015 et 2017. L'objectif du programme est de fournir aux pays européens des données complètes et…"
<egg|laptop|egg> UmbralRaptop: is this just limited by downlink bandwidth, or are there deep reasons to not go anywhere near the diffraction limit
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<raptop> FoV?
<raptop> I mean, I'm under the impression that anything optical is diffraction limited if you want it to be
<egg|anbo|egg> the swath for VIIRS is 120°
<raptop> that's a very wide FoV
<egg|anbo|egg> but the question is more why would you not want it to be diffraction-limited
<raptop> !wa 5e-7/0.19*180/3.14159*3600
<raptop> ;wa 5e-7/0.19*180/3.14159*3600
<raptop> bah
<egg|anbo|egg> tfw no kmath
<egg|anbo|egg> !wa llaby
<raptop> call it half an arc-second for nyquist-sampled diffraction limited pixels
<raptop> so, uh, 864000 pixels wide
<raptop> VRO's raft is only like 56000 pixels on a side
<raptop> Anyway, you could easily end up with gigapixel images in the visible
<egg|anbo|egg> yeah so VIIRS/Suomi NPP does 7.7Mbps
<egg|anbo|egg> but I am calculating 2300 pixels * band / day
<egg|anbo|egg> which seems wrong, since I don’t think they have 5000 bits per pixel
<egg|anbo|egg> that would be some truly fine grained radiometry
<egg|anbo|egg> source for the data rate: https://www.jpss.noaa.gov/viirs.html
<galois> title: Joint Polar Satellite System
<egg|anbo|egg> 2300 pixels * band / second, not day
<egg|anbo|egg> but still, that’s too low to get to that data rate
<egg|anbo|egg> pixel rate estimated as (3040 km * 7.5 km/s) / ((750 m)² * 16 + (375 m)² * 5)