[HN Gopher] NASA believes it understands why Ingenuity crashed o...
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NASA believes it understands why Ingenuity crashed on Mars
Author : thunderbong
Score : 40 points
Date : 2024-12-11 18:01 UTC (2 days ago)
(HTM) web link (arstechnica.com)
(TXT) w3m dump (arstechnica.com)
| chtitux wrote:
| Getting the device speed right seems way more difficult without a
| Global Positioning System.
|
| Hopefully it will eventually be deployed [0]
|
| [0] https://techport.nasa.gov/projects/146938
| anothertroll123 wrote:
| Doubtful and unnecessary
| mannyv wrote:
| They need to drop beacons on all the surfaces to make navigation
| easier.
| tonyarkles wrote:
| You know... something I'd never really considered before now is
| that Mars has an absolutely pristine RF environment that would
| be pretty much impossible to find anywhere on Earth. I'm not
| sure how the overall noise floor would look with the lack of a
| global magnetic field but I would guess that you could set up a
| really great positioning system using small low-power beacons
| since you could use any frequency you want instead of trying to
| compete with, say, all the 2.4 and 5GHz noise on Earth.
| throwup238 wrote:
| It's been studied somewhat, at least with satellites:
|
| _> Assuming a dish antenna with 1-m diameter, for a
| downward-looking antenna the total noise temperature is about
| the same as the Earth's for all frequency bands of interest,
| with +-15 percent deviations. For an upward-looking antenna,
| the noise temperature is less than half that of Earth._ [1]
|
| [1] https://ipnpr.jpl.nasa.gov/2000-2009/progress_report/42-1
| 49/...
| PittleyDunkin wrote:
| > In short, the helicopter's on-board navigation sensors were
| unable to discern enough features in the relatively smooth
| surface of Mars to determine its position, so when it touched
| down, it did so moving horizontally.
|
| I'm a little surprised there isn't something more accurate than a
| camera for this.
| tonyarkles wrote:
| That's actually a pretty hard problem when you don't have a GPS
| constellation to assist you. Accelerometers, gyros, and
| magnetometers are used on Earth but all of them need
| calibration and drift compensation. We don't really have much
| available for sensors that can directly detect position or
| velocity, it's all estimated by double integrating acceleration
| data (which has noise and bias). On Earth most UAVs use GPS as
| a coarse position sensor and can use that to correct for
| accelerometer error but if you don't have that constellation a
| camera is probably your best bet.
| bri3d wrote:
| The latest UAVs also use ToF LIDAR and SLAM for GPS-rejected
| navigation / inertial dead reckoning correction. I'm not sure
| that would work well on Mars either, though, as the
| environment might be too featureless for that approach also.
|
| I think the best approach would probably be to equip the
| "base station" / lander with an RF beacon. Ideally, you could
| drop some RF beacons throughout the environment as you went,
| but even a single beacon with some directional receivers on
| the drone should work pretty well (here, the featureless
| environment becomes a benefit as you have to contend much
| less with radio reflections).
| tonyarkles wrote:
| SLAM is likely exactly what they were doing on Mars (it
| falls apart if there's no image features to register
| against on the ground) and ToF lidar works great for
| vertical position and velocity but doesn't help much for
| horizontal position or velocity if there isn't much terrain
| variability for the lidar to reflect off of nearby.
|
| 100% agree on the RF beacons. You might not even need the
| directional antennas. Using things like RSSI might be
| enough to augment the local sensors. Alternatively having a
| digitally-controlled phased array could probably result in
| quite excellent positioning.
| bri3d wrote:
| > SLAM is likely exactly what they were doing on Mars
|
| I think the system on Ingenuity just used feature
| detection based 2D optical flow rather than a more full-
| scale 3D environment-reconstruction type SLAM setup.
| Which is fine since neither would work in a blank
| environment like that.
| wafflemaker wrote:
| I don't really get why there is no constellation around Mars
| already. That's literally the first thing you do when sending
| a mission to another planet - establishing a simple 3 sat
| comm network.
| ceejayoz wrote:
| We have a comm network there - several satellites serve as
| comm relays. https://www.nasa.gov/centers-and-
| facilities/jpl/the-mars-rel...
|
| They just aren't GPS satellites. At some point we'll likely
| get some there, but it's a) a good amount of payload and b)
| not something we've _really_ needed there so far.
| michaelt wrote:
| GPS uses a lot more than three satellites (you need at
| least four a fair bit above the horizon to be able to
| navigate), and they have to be in different orbits.
| Earthbound GPS also uses a network of base stations at
| known locations to figure out the satellites' locations.
| mandevil wrote:
| A comm sat network is very very different from a
| _positioning_ satellite network. You 'll notice that here
| on earth those missions are done by very different
| satellites in very different orbits, they are not
| substitutes for each other.
|
| Every NASA science mission to Mars orbit for over 20 years
| has had a communications relay on it, for relaying messages
| from rovers back to Earth, but the one in the best orbit
| for communications (Mars Odyssey) is also the oldest and
| most likely to fail. The other NASA science orbiters (MRO,
| ME (ESA), MAVEN) all also have relays, but the orbits all
| leave something to be desired for communications purposes
| (they are in the right orbits for answering their
| scientific questions, e.g. MAVEN is in a highly elliptical
| orbit for studying the Martian atmosphere).
|
| There was a proposed Mars Telecommunications Orbiter- a
| satellite whose primary mission would have been beaming
| back information from rovers on the surface- proposed back
| around 2005, but it was canceled in a budget crunch, when
| actual science producing satellites were prioritized. That
| would have been in the right orbit.
|
| Building a positioning satellite network around another
| body is going to be significantly harder, incidentally.
| Even something like TRANSIT (aka NAVSAT) (1) is going to be
| significantly harder on another body because we haven't
| mapped their gravity fields due to density fluctuations as
| well, the upper atmosphere is not as well studied for drag
| effects, and we don't have fixed locations that can
| determine orbital parameters very precisely by either
| visual or radar observations after every orbital
| maintenance burn. Small uncertainty in orbital position
| lead to gigantic uncertainty in your position, and none of
| the techniques we use here on earth to remove that
| uncertainty would work around Mars.
|
| 1: Instead of the "see multiple atomic clocks and use
| triangulation and the speed of light to determine distance
| to each of them, then our location from their known
| locations" which is how all modern satnav systems work,
| TRANSIT used a single satellite passing nicely overhead
| every so often. When it was right above you, you could
| listen to the Doppler shift and know when it reached
| exactly the zenith above you. If you knew it's orbit very
| precisely you could tell where it was in space when it
| reached that zenith, and therefore where you were.
| magicalhippo wrote:
| Since it's communicating with the rover, I was thinking it
| could use latency and/or Doppler effect as an input to narrow
| down the position, assuming the rover knew where it was,
| potentially by getting told by the satellites we have there.
|
| However I assume that would require special radio software,
| and they were using commercial Zigbee modules. In addition, I
| guess perhaps the helicopter and potentially rover wouldn't
| have accurate enough oscillators for this to be viable in any
| case.
| f33d5173 wrote:
| You can use radar or similar technologies to determine
| velocity. Point it straight down and you can see how fast
| you're falling. Point it at an angle, subtract vertical
| velocity, and you have horizontal velocity.
| adriancr wrote:
| alright, radar at angle, unknown surface but all looks the
| same, no landmarks to track against, unknow radar
| properties of surface, how do you translate that into
| directional speed?
| magicalhippo wrote:
| > I'm a little surprised there isn't something more accurate
| than a camera for this.
|
| Another thing to keep in mind is that the helicopter was made
| using off-the-shelves parts[1], including for avionics, to see
| how well they held up on Mars.
|
| As such I think it did amazingly well.
|
| [1]:
| https://en.wikipedia.org/wiki/Ingenuity_(helicopter)#Design
| Brian_K_White wrote:
| I thought one of that devices explicit experimental purposes
| was to intentionally use relatively commodity hardware, still
| NASA-fied but not nearly as much as usual, and see how far you
| can actually get with something relatively cheap and almost
| off-the-shelf. That's why it runs linux for instance. So an
| ordinary phone camera (relatively, relative to other nasa
| hardware) would be expected and deliberate.
|
| So it never had a goal to last as long as possible, it had a
| goal to see how long it lasts when you don't sink 100 million
| into every screw.
|
| I thought anyway.
| pnw wrote:
| On the bright side, the mission goal was five flights and
| Ingenuity completed 72 flights in three years!
| bpodgursky wrote:
| It was genuinely impressive and I don't mean to downplay that,
| but NASA always massively lowballs "mission goals". In
| practice, probes either fail completely, or wildly outperform.
| cogman10 wrote:
| I assume it's because the things that make stuff fail early
| are also the things that if addressed will make a project
| live for 75 years.
|
| For example, solar panels for the rovers are overbuilt
| because you can't clean them if a chance dust storm is a bit
| too dusty. But that overbuilding also means that as long as
| the panels stay reasonably free of dust, the rover will last
| a long time.
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