raptop 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
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<mofh>
e_14159: ?
<mofh>
err
<mofh>
egg|work|egg: ?
<mofh>
mlbaker: I mean yes, BPIT suffices to give you Hahn-Banach,
<UmbralRaptor>
mlbaker: a semiring is for when Sauron declares a constitutional monarchy, right?
<egg|cell|egg>
Mofh: MEOW
<egg|cell|egg>
miau
<egg|cell|egg>
喵
<mofh>
egg|cell|egg: MEOW
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<mofh>
should I stare at Meeus (1992)?
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<mofh>
miaou
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<UmbralRaptor>
meeowus (1992)
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<egg|cell|egg>
Mofh: have you considered: car
<egg|cell|egg>
Um
<egg|cell|egg>
s/r$/t/
<galois>
egg|cell|egg meant to say: Mofh: have you considered: cat
<mofh>
I do not have a particular desire to consider cars
<mofh>
(nor cdrs, for that moment. cats OTOH are eggstremely okay)
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<egg|laptop|egg>
mofh: hm, i'm thinking about the meeus thing about the equinox-to-equinox time not being the same as the tropical year and I'm wondering if I should do the same for the nodal period of an artificial satellite
<egg|laptop|egg>
or whether this is irrelevant considering things like resonances with higher degree and order terms
<egg|laptop|egg>
periapsis-to-periapsis time doesn't seem more stable than node-to-node time on arbitrary artificial satellites though, I'm getting T = +4.0520(14) × 10^+4 s and T☊ = +40543.634(31) s from 12 SPOT-5 orbits
<egg|laptop|egg>
UmbralRaptop: mofh: how are the 0s of the equation of time chosen
* UmbralRaptop
doesn't know. mofh?
* egg|laptop|egg
pokes the mean sun with a stick again
<UmbralRaptop>
meenus sun
<egg|laptop|egg>
okay so the mean sun coincides with the true sun when the perihelion coincides with the equinox and the sun is there
<egg|laptop|egg>
aaaaaaa
<egg|laptop|egg>
at perihelion meeus's first fictitious sun coincides with the true sun, but the mean sun coincides with that first fictitious sun only at its crossing of the equator......
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<egg|laptop|egg>
mofh: meow
<egg|laptop|egg>
B787_300: do you know if JPL IOM 312/95.5-4353 can be found somewhere
<egg|laptop|egg>
Allison, M., and J. Ferrier: Planetocentric solar coordinates, including efficient recipes for seasonal/diurnal timing on Saturn and Titan. Unsubmitted paper. << STABBITY
<UmbralRaptop>
djdjjjssakad
<egg|laptop|egg>
B787_300: also JPL IOM 312/85.5-2397
<mofh>
17:49:31 < egg|laptop|egg> UmbralRaptop: mofh: how are the 0s of the equation of time chosen
<mofh>
I actually do not know, come to think of it. That's a good question. I think "Calendrical Calculations" had a derivation, I forget the author.
<mofh>
(oh, dershowitz&reingold).
<UmbralRaptop>
hrm. Meenus also has a book that might be relevant. Give me an hour?
<mofh>
Yeah, I seem to recall the same. Meeus (1992) perhaps?
<mofh>
Also likewise.
<mofh>
Scientific computer programming is great b/c some days your task winds up being "okay, here is this special function. it is defined only by 20 Chebyshev series in piecewise fashion (each series is valid over an interval of length 0.25, the whole thing over [0,5[), there is no documentation of *what* it is, and you finally fixed the transcription errors so that it's actually approximately smooth over the
<mofh>
whole interval. Hopefully this should ...
<mofh>
... *finally* suffice to figure the stupid thing out?
<mofh>
It's asymptotically x^2/sqrt(π) near 0 and asymptotically basically D⨧(x) for x > around 4 or so (in fact the difference between it and D⨧(x) are < DBL_EPSILON for x > ~7.5)
<mofh>
Everything in between there makes absolutely no sense, tho.
<mofh>
...
<mofh>
!u ⨧
<galois>
⨧: U+2a27 PLUS SIGN WITH SUBSCRIPT TWO
<mofh>
i have two squestions: one, why is that even a unicode character, two, i asked for a subscript plus sign, how the hell did i get that?
<mofh>
(i mean the answer to the latter is prolly X11 input systems are all horrible, but...)
<UmbralRaptop>
maybe you're cursed?
<SnoopJeDi>
!8
<galois>
SnoopJeDi: no
<oeuf>
mofh: meow
<oeuf>
mofh: A Post-Pathfinder Evaluation of Areocentric Solar Coordinates with Improved Timing Recipes for Mars Seasonal - Diurnal Climate Studies is possibly relevant
<oeuf>
mofh: p. 8-9
<SnoopJeDi>
relatedly, I'm currently re-reading Red Mars, and just last night passed through the first long digression on Martian timekeeping
<oeuf>
mofh: """A similar method was adopted by 9 Lee (1995) for the Mars Surveyor Project, fitting the FMS rate (or tropical mean motion) to successive passagesof the Mars vernal equinox for the years 1996, 1998, 2000, and 2002, then calibrating the FMS angle at a particular epoch by its consistent evaluation for an average of the areocentric longitude at the successive Mars perihelia in 1996, 1998, and 2000. These approaches
<oeuf>
to the FMS determination have the advantage of avoiding any explicit reliance on the classical mean orbital elements, and reflect a small but significant difference between ntrop and nanomas apparent even over a small number of orbits. Aside from the limits of these fits to their assumed short temporal intervals and their apparent neglect of aberration, however, these approaches do not in principle take the most accurate
<oeuf>
account of a very small variation for the seasonal repetition of different values of the L s, as evaluated below."""
<oeuf>
"ntrop and nanomas" should read "n_trop and n_anom as"
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<UmbralRaptor>
bleh. Meenus does not give reasons for his numbers
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<B787_300>
Egg are they not find able on Google?
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<B787_300>
You could get UmbralRaptor to try to FOIA them from JPL if they cant be found on google
<B787_300>
I assume you have tried searching through NTRS though
<B787_300>
egg|laptop|egg: see above^
<egg|laptop|egg>
most JPL IOMs don't seem to be on NTRS for some reason
<egg|laptop|egg>
(I mean, I guess it says N and not J)
<B787_300>
I mean jpl is part of nasa kinda
<UmbralRaptor>
B787_300: I'm bow imagining a FIOA rejection claiming that the relevant ephemeris need to be classified, or something
<UmbralRaptor>
s/bow/now/
<galois>
UmbralRaptor meant to say: B787_300: I'm now imagining a FIOA rejection claiming that the relevant ephemeris need to be classified, or something
<B787_300>
But yeah if you have struck out on Google and ntrs it might be FOIA time
<B787_300>
I'll look around for it on monday at work and see if I can find it
<B787_300>
egg|laptop|egg: that is werid that it isnt on NTRS
<egg|laptop|egg>
I mean, I can't find it, maybe it is and I'm bad at NTRS
<B787_300>
Have you asked the librarians at your library if they can find it
<egg|laptop|egg>
uh
<egg|laptop|egg>
i mean yes, technically there *is* a library in the 2000-inhabitant town 5 km away
<egg|laptop|egg>
B787_300: i'm very much in the boonies at the moment, and even when i'm back in zurich, i'm not in academia anymore
<B787_300>
Oh
<B787_300>
Pity
<egg|laptop|egg>
(should probably go back eventually but)
<B787_300>
Why do you need a document from 1985
<SnoopJeDi>
what's wrong with 1985
<egg|laptop|egg>
to figure out how they compute the mean sun from ephemerides, because that seems like the nicest thing to do for an arbitrary planet in Principia
<egg|laptop|egg>
the standard way is to have an analytical model of the motion of the planet and to use that, but that's not going to happen with principia
<egg|laptop|egg>
I think the 1995 memorandum would be the most interesting one here
<B787_300>
SnoopJeDi: other than being 1 year younger than me? Nothing
<egg|laptop|egg>
B787_300: also trying to nudge some RO folks into designing experiments/contracts whose constraints are based on observation conditions rather than orbit, so that the choice of orbit is up to the player and you get to play mission design: the game,
<B787_300>
verification over time would be hard
<egg|laptop|egg>
what do you mean
<B787_300>
say you have a misison that calls for daily coverage of a point on earth/kerbin for 2 years. how do you make sure that the sat didnt drift because principa during that time period to see if the constraints were met
<egg|laptop|egg>
B787_300: I'm not sure whether the "you" here refers to the mod or to the player
<B787_300>
both really
<mofh>
"reflect a small but significant difference between ntrop and nanomas apparent even over a small number of orbit"
<egg|laptop|egg>
if it's the mod, Kerbalism has experiments that complete over time if a constraint is satisfied
<mofh>
wait, how?
<egg|laptop|egg>
B787_300: e.g. in kerbalism as-is you can have an experiment that only progresses in full view of the sun
<egg|laptop|egg>
and it would be easy to add "with the sub satellite point within 100 km of cap Canaveral under an illumination between 60 and 85 degrees" or whatever
<egg|laptop|egg>
(geographic constraints probably belong in the contract rather than the experiment but SirMortimer who develops that thinks this is feasible)
<egg|laptop|egg>
B787_300: as for how do you get a sat there, well, if you want daily coverage of a point with good lighting as you said, 1-day phased heliosynch orbit
<egg|laptop|egg>
(type FormoSat-2)
<B787_300>
egg|laptop|egg: does principa have a built in orbit preview so you know what you need to target?
<B787_300>
or is the poor player going to have to get STK or look up the equations
<egg|laptop|egg>
> does principa have a built in orbit preview so you know what you need to target?
<egg|laptop|egg>
right now it just has the prediction, so long-term analysis doesn't work; that still gives you a map if you plot in the ECEF frame though
<egg|laptop|egg>
I'm working on an analyser that will tell you about the precession and phasing and sun-synch properties of your orbit
<egg|laptop|egg>
that way you can know that your orbit is sun-synch with ascending node at 22:30 without having to eyeball angles in earth-centred sun-direction-fixed frames
<egg|laptop|egg>
B787_300: the sun-synch orbits with AN 22:30 MST sure have a lot of stuff on them
<B787_300>
isnt that the A Train?
<egg|laptop|egg>
B787_300: A-train is 13:30
<egg|laptop|egg>
+ WorldView-1, and Hélios-lA, -lB, -2A and -2B
<egg|laptop|egg>
B787_300: 22:30 (or 21:30) has Landsat -1 to -7, EO-1 and Terra, SPOT -1 through -5, ERS-1 and -2, Envisat, MOS-1 and -1B, JERS-1, ADEOS-1 and -2, ALOS, IRS-1A, -1B, -1C, 1D, -P2, -P3, Resourcesat-1 and -2, Cartosat-1, -2, -2A, IMS-1 and TES, Resurs-O1-4, CBERS-1,-2,-2B, THEOS, FormoSat-2, HJ-1A, -1B, SAC-C, PROBA, EROS-A1
<egg|laptop|egg>
oh yeah you also have Ikonos-2, QuickBird-2, WorldView-2, GeoEye-1
<egg|laptop|egg>
B787_300: whereas 13:30 is just A-Train (7ish satellites at most) + 4 french spysats + WorldView-1
<egg|laptop|egg>
B787_300: 10:30 is very calm: 2 Koreans and 2 Brits (Arirang-1, -2, UK-DMC, UK-DMC2)
<egg|laptop|egg>
B787_300: 22:30 means you see the north hemisphere between 10:30 and 11:30 (morning), 13:30 is between 12:30 and 13:30 (afternoon, like the A-train)
<egg|laptop|egg>
apparently morning is preferred for meteorological reasons
<B787_300>
calmer air so sounding is more effective?
<egg|laptop|egg>
might just be afternoon haze
<egg|laptop|egg>
Capderou doesn't go in depth, just mentions that meteorological concern break the tie