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    Visible Light Detector
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    West Java
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    Transport, Space !

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  1. Welp, sadly the 2nd stage didn't light up at all. Looking back in the stream at the 2nd stage sep/engine ignition point, the commentators (?) knew it went wrong as well I think. They mentioned they were glad it launched but since it fails mid-way they can't say it's a success.
  2. Fairing sep Switching to map (ground trajectory) view, no onboard cams I suppose. Second stage staging EDIT : I'm actually quite surprised by the launch trajectory, as it differs quite a lot from the operational ground track... I suppose it takes quite a transfer orbit for it to reach final position. The payload is a replacement for the QZS-1 satellite launched in 2010. QZS-1 through 3 goes on this orbit (different mean anomalies), QZS-4 is geostationary instead.
  3. Launched ! I suppose the weather is rather clear here because the typhoon is located quite a way away. Fairly often they'd "attract" other bad weather systems around into it, clearing the extended surroundings.
  4. Epsilon 5 rocket launch on October 1, 2021 : They put up like a ton of videos on the thing over on their channel, I don't think the thread would survive all the embeds EDIT : Today (October 1st 2021)'s launch attempt was suspended, apparently over problems on the GSE. Will have to look again when will they plan the next launch attempt.
  5. ... That being said, GNSS satellites (and other satellites) still derive their final position from a ground observatory. I've heard that at least one collaboration have up to 500 observatories - if they could be a fairly accurate source while providing enough high-accuracy coverage for ground-based positioning signals, maybe it'd work ? idk.
  6. MMX video explaining what they're expecting from D-type asteroids :
  7. GNSS Receivers does not transmit any signals - they just compare the clocks they have on-board (which is synced - value-wise when first started with terrestrial time signals, and step/rate-wise as long as the receiver is turned on) with the continuously transmitted messages from the satellites. Satellite position is both contained in the transmission and there are backup ephemeris within the receiver that allows operation under degraded accuracy. By comparing the time right now and the time at transmission it's possible to tell how far away you are from the beacon, and if you have the data from at least 3 beacons the intersection of the 3 circles of radius/distance it gives you your position - roughly (in reality I think you need a 4th one due to 3-dimensional sphere rather than circles that it produces). Directional transmission is available but obviously only certain receivers get this treatment (like some random joe's phone probably won't but military airplanes probably would). Yes, and with more fixed transmission beacons you'd increase the accuracy. The problem is that the world isn't a single country, and there're seas. They had >75 LORAN-C stations to serve mostly the northern hemisphere's seas (none would work well in-land since that wasn't the focus) - there're only 31 GPS satellites on-orbit right now providing coverage anywhere on Earth (excluding mines and tunnels), with merely 1/20th the error (20x more accurate).
  8. Maps only tell you the relative positions of features on the surface of the Earth - at no point does it tell where you are exactly. You can't use a map to adjust for errors - you gotta find a reference with 'known' positions then try to determine where you are. And since the comment was made in reply to airborne positioning beacon it's kinda useless IMO if you have a beacon that in itself have to derive their position from a completely different system already all the time (granted GNSS satellites does this - they're tracked by ground stations with known 'fixed' locations - but as with most celestial bodies space ephemeris are pretty accurate). If those airborne positioning beacons have to derive from ground stations we'd probably need a ton more ground stations (since they'd need one at line-of-sight), so much that it'd probably be easier to use the ground stations directly, and if they derive from GNSS themselves why not just use the GNSS directly ? Well GNSS is the advancement in technology we've finally arrived at. It's suddenly only 1/20th of it's predecessor, and that was with SA. EDIT : Although to add, why I brought up the datum as well, is because we haven't been using a unified global datum until GNSS comes along.
  9. Yeah but you can very easily describe their trajectory using a geodesic, which you can't do for a flying or floating thing in the air. That's why TLEs have been around since ages ago. And what are you basing that maps on ? Ground beacons measured with chains and triangulation ? It's better to just use ground beacons then... GPS/GNSS literally eliminates all of this, look up the recent proposed changes on geodectic systems (at the very least gravitational models), it's all based on the satellites' geodesics.
  10. If it's not fixed to the ground, or it can't be expressed in TLE that doesn't need to be changed every so often, I don't think you can use it to calculate your position wrt the Earth, unless you only want relative positions to the beacon or something. Also by "cheap" I mean to the end user. Sure yes some government's tax money had to pay for the satellites and maintaining them, but even if it never sees direct financial returns, much like the idea of weather reconnaisance satellite/stations - or emergency and disaster relief - it's just one of those things you don't do and expect any sort of financial incentives back. Though arguably it's still better than most other alternatives (like with ground stations who owns the land becomes important).
  11. MMX project mission overview (again) : EDIT : Also, Epsilon 5 launch date has been set on October 1, 2021 :
  12. LORAN too ? But actually even back in the age of CDMA and GSM mobile signals (so 2G) it was possible to roughly locate where you are. I still remember during our yearly mudik trip those nokia phones from the early 2000s would tell you which city are you in/passing through (I believe it was down to which district but not sure). These days I presume if you designate every 4G and 5G transmitter with a GPS coordinate and/or equip it with a GPS base receiver (the stuff that calculates their position for years on end stationarily to achieve extremely high precision) you can easily lose the GPS satellite and just rely on that maybe for a decade or two. But GPS/GNSS is always going to be far superior and cheaper. There's a reason GNSS approach minimums are equal to ILS Cat I approach minimums.
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