Matijevic Hill detailed survey, Sol 3153 - 3290 Options

[PaulM]

The monthly report is out:

Planetary Society Report

I likes the enhanced CRISM view of Cape York. The area of smectite clay is realy clear in that picture. I wonder when the enhanced view of the clays on the Southern side of Solander point will become available?

I liked the statement "As soon as conjunction is over, we'll be heading south to Solander Point as quickly as we can" . I wonder if that means that Oppy will head on the shortest path across the Endeavour crater floor to the base of Solander point. From that position Oppy could climb up to the clays and reach the clays within a few months.

I had assumed that Oppy would travel around the rim of Endeavour Crater and climb the Northern face of Solander Point, where there are no clays. By the time Oppy had reached the summit of Solander Point it would be Autumn and Oppy would need to wait until the following spring before decending onto the clays from above.

Either way I hope that Oppy's wheel does not break when she is on the interesting Southern face of Solander Point because she could not survive a winter resting on those clays.

[fredk]

Check out our discussion of that enhanced crism view starting with this post. It may be that the red region is just the ground-based determination of the Whitewater outcrops.

[Phil Stooke]

I can add more about the red region now. Ray Arvidson explained it at LPSC. The image does not show that patch however it is processed. Ray himself looked at the spectrum of each pixel in that area, and where he found the subtle indicators of the clays he was looking for, he made those pixels red. The distinction was too subtle to show up in the image itself but could be teased out that way. When he finished his map Opportunity was driving south just below the 'red' patch, and Ray had them slam on the brakes (so to speak) and take a hard right up the hill. After their circuit of the hilltop it was clear that the red patch matched the Whitewater unit very closely.

I don't think this precludes other clay outcrops on Cape York, as I don't know exactly how far Ray's mapping extended.

Phil

[ngunn]

where he found the subtle indicators of the clays he was looking for, he made those pixels red. The distinction was too subtle to show up in the image itself but could be teased out that way.

A very insightful post Phil. It has to be said that anything 'teased out that way' comes with a caveat, and the image itself as published has to be described as misleading, given the way it was made. It doesn't show any smectite outside the area directly inspected by Opportunity. Why not? I'm sure he believes very strongly in the case he is making and in fact (FWIW) I accept his conclusion.

[elakdawalla]

Only in the sense that any reading of scientific data comes with a caveat. Using images to represent hyperspectral data is good for showing spatial relationships but positively awful for displaying the actual spectral information content. Hue in images can show you variation along a maximum of 3 axes (red, green, and blue). CRISM images can contain up to 500 spectral bands. There's no way to represent all that information in a single color photo. So the idea of looking at the spectrum at each pixel and identifying an important spectral feature and coloring in the pixels that have that feature is a perfectly valid thing for a spectroscopist to do.

[ngunn]

All true, the science is not in question, my respect for the scienists is enormous. Also he's not to blame for the fact that the image went out months ago when the abstracts were posted and was discussed here with the limited information available to us at that time. Even so, I think hand-coloured pixels should be flagged up as such. He did that in his conference presentation but we wouldn't have known that (outside the conference) without Phil's post. I'm still not sure why no red pixels appear outside the area traversed by the rover when the CRISM smectite patch is much larger, especially southward. It would have been more convincing had this been done.

[serpens]

You gotta admire the methodology and perseverance that identified the potential target area although 5m per pixel would make for overlap, making localisation of what seems to be limited occurrence of smectite a bit difficult given Opportunity’s limited ability to ground truth the area. The APXS results imply aqueous alteration but unfortunately the identification of Whitewater as the source of CRISM smectite indications must remain a hypothesis.

[stevesliva]

Hue in images can show you variation along a maximum of 3 axes (red, green, and blue). CRISM images can contain up to 500 spectral bands. There's no way to represent all that information in a single color photo.

Unless you're a mantis shrimp.

[Phil Stooke]

Get ready for more action soon! Although Curiosity will be in conjunction mode until the end of the month, brave little Opportunity will be back in action in only a few more days, and unless something very interesting has suddenly turned up, it will be time for another road trip.

Phil

[xflare]

Are they just being more cautious with Curiosity then? Conjunction is so boring for us, thank goodness its only every two years haha.

[PaulM]

I can add more about the red region now. Ray Arvidson explained it at LPSC. The image does not show that patch however it is processed. Ray himself looked at the spectrum of each pixel in that area, and where he found the subtle indicators of the clays he was looking for, he made those pixels red. The distinction was too subtle to show up in the image itself but could be teased out that way. When he finished his map Opportunity was driving south just below the 'red' patch, and Ray had them slam on the brakes (so to speak) and take a hard right up the hill. After their circuit of the hilltop it was clear that the red patch matched the Whitewater unit very closely.

If Ray's mapping is objective then I presume that a computer program could be written to extend the map of smectite clay outcrops over a much larger area.

Such a map would allow it to be decided which side of the rim Oppy should explore as it heads South. If I remember rightly, clays have been detected both on the West side and on the East side of the hills of the rim and so in the long run a decision must be made which set of clay deposits to examine.

[serpens]

I think figure 1 of this article is the map you refer to.

www.planetary.brown.edu/pdfs/3954.pdf

Phyllosilicates primarily on the inner rim. 'Teased out' gives the impression of a somewhat subjective/intuitive judgement as part of a laborious analytical exercise. Wray's analysis indicates the possibility of a more extensive deposit on top of Cape York but Opportunity could drive across a clay rich area without the ability to identify it as such.

[Vultur]

Are they just being more cautious with Curiosity then? Conjunction is so boring for us, thank goodness its only every two years haha.

I'm curious on the length of solar conjunction too. The sun is only 1/2 degree (out of 360) wide on the sky, so why does solar conjunction occupy more than 1/720 of the time? Can the communication equipment not be pointed closely at the sun, and if not why not? I was sort of under the impression that the sun wasn't an incredibly strong radio emitter, but maybe it is...

[djellison]

It's simply a case of reliability. You do not want to uplink commands only for the vehicle to not receive them properly and thus throw itself into an X-Band fault or other safe mode.

This document on MRO : http://descanso.jpl.nasa.gov/DPSummary/MRO_092106.pdf : states

"An X-band link using BPSK begins to degrade near a 2-deg SEP angle."


On DS1 : http://descanso.jpl.nasa.gov/DPSummary/All_Article2.pdf

"For DS1, X-band up- and downlink, we considered an angle of 5 deg as the minimum at which to expect no degradation, and 3 deg as the minimum at which reliable communications could be planned. From October 20 to December 3, 2000, the angle was less than 5 deg, and from October 29 to November 25 it was less than 3 deg. The minimum angle was less than 0.5 deg during a scheduled pass on November 14, 2000. The 11-year solar cycle was near its maximum"

[TheAnt]

Indeed, even though the Sun is relatively quiet in the band used for radio communication, a single outburst could change a command into something quite undesirable. And on top of it the operators would have a very hard time to know which command have been randomly changed. So yes, it's about reliability and safety as far as I understand this also.