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
<B787_300>
egg|laptop|egg: to give you an idea of what you need, over 1 year a 40 kg sat with a area od 3 m^2 in a 474 circular sun sync at 97.3 deg inc you need 34.57 m/s every year
<egg|laptop|egg>
right, my question is more whether it's done as 95 mm/s every day if close recurrence is needed or whether that level of precision is infeasible
<B787_300>
how good is the ground network supporting the satellite? IE how does the satellite know it is not in the right orbit
<B787_300>
And what is the satellite doing... if it is doing electro optical imagery you might not want to be thrusting while the aperture is open.
<egg|laptop|egg>
so right now I'm looking at 福爾摩沙衛星二號 (Formosat-2, formerly ROCSAT-2)
<B787_300>
Similarly you will have to stop ops to orient the engines in the right way unless you are doing funky stuff with engine mountings
<B787_300>
Oh and what is the minimum pulse on the engines?
<B787_300>
Because that will effect how often you can do stationkeeping
<egg|laptop|egg>
the altitude was about 890 km, the thing had a 1-day-recurrent sun-synch orbit passing over taiwan every day, and I have no idea what engines it had
<B787_300>
egg|laptop|egg: I highly doubt they maneuvered once a day... maybe once every week or 2 because who really cares if you drift a couple minutes before or after the nominal design time?
<egg|laptop|egg>
yeah I guess that makes sense
<B787_300>
Plus that would probably put the required dv in a much easier to hit range for chemical thrusters
<egg|laptop|egg>
for TOPEX/Poseidon it seems they keep the ground track to within < 1 km of nominal
<B787_300>
Are those part of the A train?
<egg|laptop|egg>
no, but it was in tandem with Jason-1 at some point
<egg|laptop|egg>
(which was then itself in tandem with Jason-2, but by then TOPEX/Poseidon was decommissioned)
<egg|laptop|egg>
it seems that over 1993-1999 TOPEX/Poseidon had just 13 OMMs?
<egg|laptop|egg>
at 1 300 km alt.
<egg|laptop|egg>
and apparently that was enough to keep it within 1 km of the nominal track
<egg|laptop|egg>
"MANEUVER ERROR MODEL ΔV (Fixed) 0.013 mm/s."
<egg|laptop|egg>
(that's for TOPEX/Poseidon)
<egg|laptop|egg>
and the OMMs 2 through 9 are < 5 mm/s
<egg|laptop|egg>
(from Bhat, Shapiro, Frauenholz, and Leavitt, TOPEX/Poseidon orbit maintenance for the first five years, AAS 98-379)
<egg|laptop|egg>
(which I should print out and give to my cat probably)
<B787_300>
egg|laptop|egg: yeah using my calculator with JASON-1 like specs (1325 km orbit @66 deg, 500 kg mass 8 m^2 area [estimated]) the required correction for one year is 0.03 m/s
<egg|laptop|egg>
B787_300: what do you get on 890 km, 98°.77?
<B787_300>
0.06 m/s
<B787_300>
(over i year)
<B787_300>
s/i/1
<galois>
B787_300 meant to say: (over 1 year)
<egg|laptop|egg>
imaginary years!
<egg|laptop|egg>
... what is the pluralization of complex numbers, is it i year or i years
<egg|laptop|egg>
cc bofh
<B787_300>
now i will say because i havent alrready... this calculator is very simplistic and doesnt do things like seasonal or diurnal variations
<egg|laptop|egg>
yeah but it sounds like a reasonable order of magnitude
<bofh>
egg|laptop|egg: I assume i year, like all roots of unity are a singular quantity i believe.
<egg|laptop|egg>
bofh: as you know, the plural case depends on more than the numeric value though,
<kmath>
<Integrity_Guy> That feel when you’re watching the game with your homies and you all start instinctively purring and “kneading” the… https://t.co/AQvZwRnc0f
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* egg|laptop|egg
meows at bofh, whitequark, et al.
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<egg|laptop|egg>
"averaged mean inclination"
<whitequark>
warning: word may contain egg
<egg|laptop|egg>
hah
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* egg|laptop|egg
stares at the Capderou book
<egg|laptop|egg>
bofh: it writes Feng Yun-3 as 風雲三 rather than 风云三
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<oeuf>
cc rqou
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<egg|laptop|egg>
bofh: meow
<bofh>
egg|laptop|egg: so it seems like just the traditional form of the name. not sure why but I don't think it's invalid?
<egg|laptop|egg>
bofh: yes it's the traditional form
<egg|laptop|egg>
bofh: it's a PRC sat :-p
* egg|laptop|egg
pets cat
<egg|laptop|egg>
bofh: how should I measure the inclination and eggscentricity
<bofh>
measuring inclination should be easy, it's just the angle between orbital plane and ecliptic, so I think just an arctangent suffices?
<bofh>
eggscentricity... no idée.
<egg|laptop|egg>
bofh: an arctangent suffices to get the osculating eggscentricity
<egg|laptop|egg>
s/egg.*/inclination/
<galois>
egg|laptop|egg meant to say: bofh: an arctangent suffices to get the osculating inclination
<egg|laptop|egg>
bofh: and it's easy to get the eggscentricity via the usual formulae
<egg|laptop|egg>
bofh: my question is how do I define a meaningful mean inclination or mean eggscentricity (ideally one that's easy to compute from a cartesian trajectory)
<bofh>
I don't think inclinations generally vary that much without explicit stationkeeping, so honestly just using the osculating is probably *sufficient*.
<bofh>
Mean eggscentricity... I actually had to look this up, sec, I have two papers.
<egg|laptop|egg>
bofh: angle of the trajectory with the equator? max latitude? average of the osculating inclinations over an orbit?
<bofh>
average over an orbit should be more than fine
<egg|laptop|egg>
bofh: i and e both have short-period variations
<egg|laptop|egg>
the osculating elements do very much vary over one orbits
<kmath>
<AsteroidEnergy> MRO captures Insight and its two circular solar panels on the surface of Mars. The bright point of light is the SEI… https://t.co/jTag7TdoYj