Night driving for MSL? Options

[Guest_Actionman_*]

Driving at night might be better.

[djellison]

How would you conduct hazard avoidance in the dark? How much extra energy would you be spending heating the mobility system to allowable temperatures before moving?

And moreover....why might it be better at night anyway? I've attempted to drive across the sand in 40degF heat and 105degF heat....didn't change a thing.

[Guest_Actionman_*]

How would you conduct hazard avoidance in the dark? How much extra energy would you be spending heating the mobility system to allowable temperatures before moving?

And moreover....why might it be better at night anyway? I've attempted to drive across the sand in 40degF heat and 105degF heat....didn't change a thing.

You would use infrared time exposers with real time overhead data link. Or just do a short test and compare wheel slippage with the daylight data which you could after the fact..

[djellison]

You would use infrared time exposers with real time overhead data link.

The Haz and Navcam's are not IR cameras. They can not see in the dark.

https://www-robotics.jpl.nasa.gov/publicati...ne/fulltext.pdf

Their sensitivity is between 600 and 800nm. Thermal IR starts at 3,500nm

What is a 'realtime overhead data link'? Are you talking about returning data from MRO? That only happens for about a 15 minute period, twice a day, and the one-way light time is usually more than the duration of an MRO pass.

[Guest_Actionman_*]

Their sensitivity is between 600 and 800nm. Thermal IR starts at 3,500nm

What is a 'realtime overhead data link'? Are you talking about returning data from MRO? That only happens for about a 15 minute period, twice a day, and the one-way light time is usually more than the duration of an MRO pass.

1035nm MastCam with starlight is good for dune driving.

With just one peak form MRO it would be a short drive

But it could be worth it if the dune dust is more cohesive after it's cooled down.. say some time after midnight.

[Explorer1]

If there was any advantage to driving at night at all, it would have been done at least once some time in the last two years, so let's give the planners the benefit of the doubt. They're pretty good at this sort of thing, after all.

[djellison]

1035nm MastCam with starlight is good for dune driving.

MastCam can not be used for AutoNav.

MastCam will not see anything in 'starlight'

Moreover
-The MRO pass would not be long enough for an in-the-loop driving decision process.
-Earth may well not be visible during a night time MRO pass at Gale.
-The energy required to warm the mobility system to do this would be huge (if not entirely insurmountable)
-What evidence is there that 'cool' sand dunes offer more traction?

[serpens]

The silt, sand and dust that makes up the ripples seem to be mechanically locked. The surface is absolutely desiccated and empirical measurements suggest that there is no transfer of the miniscule atmospheric H2O to the regolith overnight other than very minor surface frost so there would be no ice cementing if that is what you are positing. Any minor contraction due to temperature drop would in fact reduce the effectiveness of mechanical locking such as it is. The only potential gain is that aluminium would have a marginal increase in tensile and yield strength at the very low overnight temperatures but hardly sufficient to provide mitigation for wheel damage. IMHO it would be pretty senseless to take the risk of night drives when there is no payoff.

[Guest_Actionman_*]

It will be imperative to cross dune at some point with or with out confidence. I don't see any reason to think a dune walk at night is any more dangers then at day. That should be a one move operation none stop crossing.

[Gerald]

It's more dangerous, because the ratio of slip versus wheel rotation cannot be monitored in the dark by VisualOdometry.
Hence excessive slip above a previously defined trigger level may not be detected in time.
This increases the risk to get stuck.

Early detection of excessive slip allows tracking back and choosing alternative routes, until a successful crossing is accomplished, if crossing the dune turns out to be necessary at all. South of the entry point there are gaps between the large dunes. On the way to the entry point, there is no need to drive away more than 10m from solid ground or shallow sand.

[RoverDriver]

Driving at night would be quite expensive due to the amount of heating necessary to keep the actuators warm and cozy. But mostly we could not use VO or autonav. We could just drive blind and use other parts of safety mechanisms to detect embedding but these would be very, very short drives, 10-20 meters at most. And so far I haven't heard anyone suggest that sand on Mars is more cohesive in cold temperatures. If it was, we would have seen differences in driving Spirit and Oppy, besides Curry, in Winter vs Summer.

Paolo

[djellison]

It will be imperative to cross dune at some point with or with out confidence.

It is imperative to not do something that is likely to get the rover permanently stuck. Driving into areas with questionable traction without autonav & visual odometry etc is significantly more likely to result in a permanent embedding event that would bring the mission to a premature end.

I don't see any reason to think a dune walk at night is any more dangers then at day.

Just because you don't see them doesn't mean they don't exist. It's been explained why driving in the dark would present an entirely unnecessary risk to the vehicle

[Guest_Actionman_*]

Just because you don't see them doesn't mean they don't exist. It's been explained why driving in the dark would present an entirely unnecessary risk to the vehicle

A night test is not so far fetched.

The electrostatic continuity of the subsoil will be enhanced in a sub -40 degree night environment, compared to the heat of the day... implying the possibility of a increase of cohesiveness in the soil.

[Phil Stooke]

No energy for actuator heating at night, no light for visodom, slip checks etc. Give it up! The best engineers on Planet Earth are already on the job.

Phil

[mcaplinger]

MastCam can not be used for AutoNav.

I'm not 100% sure this is true, as it was discussed as a backup in case of Navcam failure during development. But it's certainly not assured; Mastcam is not even allowed to be powered on during driving at present.

As has been pointed out, there seems to be some confusion about how night vision works. I know of three flavors: image intensification of ambient light ("starlight scopes"), near-IR with active illumination in the near-IR (seen in some security cameras, baby monitors, etc.) and thermal IR. We can't do any of those with anything on MSL and the longest exposures we could take would be unlikely to even detect the ground. Near-IR works no better than visible for ambient light -- worse, because the sensitivity of Mastcam in the near IR is quite low compared to the visible. The best we could do is use the MAHLI LEDs for illumination, but the arm can't be deployed while driving and in the stowed position the LEDs aren't pointed in a useful direction, and they're not all that bright anyway.

It's an interesting idea that slip properties might change as a function of temperature, but I don't think there's any evidence that this might be true, and I don't think there are any known examples of it for terrestrial analogs.