[X] My Assistant

[nnyspace]

So has a landing site been chosen yet, anyone know? and what is the specific (or general) location... and don't just say "up north", latitude and longitude would be better.

[djellison]

Well

"Latitude (centered): 68.2 ° Longitude (East): 233.2 °"

From http://hirise.lpl.arizona.edu/PSP_007207_2485 - which is inside the ellipse.

If you said 68 / 233 - you couldn't be considered wrong.


http://www.nasa.gov/images/content/183675m...label-hires.jpg

and

http://www.unmannedspaceflight.com/index.p...amp;#entry98551 for more.

Doug

[nnyspace]

Oh that answer my question, but it begets a new one: how big is the landing ellipses? isn't it suppose to be smaller then MERs?

[djellison]

MSL - with an actively guided entry will be smaller ( something like a 10km circle ) - but Phoenix is going to be basically the same as MER I would expect. Something like 80k x 20k - someone may be able to put my right on that though.

Dog

[dvandorn]

So, are those frost-heave cracks that form the polygonal terrain really flat, or do they present a certain amount of vertical relief?

I feel like we're trying to blind-land this thing in a garden amongst hedgerows -- it's lovely if you land in the garden, but landing on a hedgerow could ruin your whole day...

-the other Doug

[mchan]

Well, the description does say "shallow" troughs with CO2 frost. If all the frost has currently sublimated, then a new Hirise image would show the degree of shallowness.

[Phil Stooke]

To be more specific, the illustration with three ellipses shows target ellipses (roughly 100 by 20 km) for three launch dates. As Phoenix launched at the start of its launch period, only one of the three is the actual landing ellipse. It is the one running from lower right to upper left in that map. The ellipse reflects all uncertainties before launch. As they approach, the trajectory and timing will be known better, so the ellipse will shrink.

I had hoped for papers on the Phoenix site at LPSC next week, but there isn't much. Still, we should see an updated map soon.

Phil

[centsworth_II]

Looking at the HiRise landing site images, I'm reminded
of a jigsaw puzzle with no picture on it. Even with one
descent image provided by Phoenix and the capability of
HiRise to resolve the lander, I imagine it will take quite a
bit of searching before Phoenix's actual location on the
surface is found. Am I being too pessimistic?

[Phil Stooke]

A lot depends on whether any distant topography is visible. If any distant hills can be seen it will be found quite quickly.

Phil

[nnyspace]

I thought Phoenix was going to test high precision landing before MSL? I know that ran some navigation test using the Martian moons with MRO, what became of that?

[Phil Stooke]

Those tests were not for Phoenix but for future use. They require a camera to be used during approach, imaging the moons so triangulation can give an accurate spacecraft position. Phoenix can't do that because it can't take images of the moons during approach.

Phil

[nnyspace]

Ok, another question: how likely will it be that phoenix will land in the desired terrain (small boulders, crack surface, ice in range of arm, etc) in short what is the size of the optimal landing sites photographed in box A & D and how likely is it phoenix will land in that site?

[Guest_Sunspot_*]

I had a dream last night that Phoenix didn't make it down OK While still in the heat shield it started to "rock" side to side. Weird.

[mcaplinger]

Even with one
descent image provided by Phoenix...

Zero descent images. MARDI operations were deleted from Phoenix.

[Gsnorgathon]

Has anyone managed to do any radar soundings of the landing ellipse? I recall reading descriptions of the MER landing sites based on (Arecibo?) radar results, and they proved to be very accurate (from my limited perspective, at least).

Is the Phoenix landing ellipse too far north for that sort of thing? Would the radars on MEX or MRO be useful? Or is that sort of thing entirely redundant given the resolution of HiRISE?

[edstrick]

Earthbased radar at normal incidence angles is limited to the equatorial zone, between the summer and winter solstice latitudes. (Earth's orbital tilt relative to the martian orbit extends this a little.

Earthbased oblique radar can reach further north or south from the tropics. Mars is relatively "shiny" as I recall, compared with Moon and Mercury, and doesn't give high signal-to-noise data from high off-vertical viewing. There's other complications I've never fully understood. I don't know what the 2 sounding radars are telling us about the scattering properties (I've heard nothing about subsurface structures in most of the circum-polar plains) of the surface and near surface materials at high mid-latitudes and sub-polar latitudes.

[Decepticon]

I can't find any mention that a a site was picked 100 % confirmed?

Isn't it strange that no site has not been mentioned?
Or did I miss something?

[Phil Stooke]

Yes, you missed something! This is the site:

http://www.nasa.gov/images/content/183675m...label-hires.jpg

See the posts above, especially mine in Post 7. I expect we'll get more details close to the landing date. In this image, the ellipse running from lower right to upper left is the actual landing ellipse - the other ellipses were for different launch dates.

Phil

[centsworth_II]

Yes, you missed something!

Thanks. Speaking for myself, I think the confusion was that it was said that
adjustments could be made to the landing site during the first two course corrections
if needed or desired. I take it there were no adjustments made, but I don't recall
any official announcement that the original site was being retained.

edit: But since your #7 post was long after the second course adjustment, I guess the
possibility of change was already moot.

[Spirit]

Could somebody provide a global map of Mars with the landing spot marked on it? I don't have a map of Mars with coordinate grid.

[Stu]

Could somebody provide a global map of Mars with the landing spot marked on it? I don't have a map of Mars with coordinate grid.

Here ya go, best I can find quickly...



... or if you want my fancy Outreach version...

[SkyeLab]

Folks,

I had a bit of a tinker to try and come up with a possible view from the Phoenix lander using some Earth Arctic imagery as a starting point.

What do you think?

Artistic impression of the view from the Phoenix landing site.
Credit: Brian Cameron

Adapted from "Polygon-shaped features in the Dry Valleys."
Credit: David Marchant / National Science Foundation

Website containing starting image: http://www.nsf.gov/od/lpa/news/03/pr03149.htm

Direct original image link:

http://www.nsf.gov/od/lpa/news/03/images/polygons_cen.jpg

Enjoy !

Brian

Attached thumbnail(s)

 

[Stu]

Nice pic Brian, and a gorgeous place, but Peter Smith said in the spacEurope Q&A (replying to one of my questions, actually):

There are few slopes in the neighborhood and the horizon should look extremely
flat, no hills... Finally, the site is a shallow valley and has undergone erosion which may leave signatures.

[SkyeLab]

Thanks Stu,

Yeah I know it is probs a bit too hilly but I guess it is my Scottishness showing through ;-)

However, what do you make of the near ground polygons with ice?

Even more impressive in the original pic by David Marchant of the NSF.
http://www.nsf.gov/od/lpa/news/03/images/polygons_cen.jpg

Cheers

B

[Stu]

Thanks Stu,

Yeah I know it is probs a bit too hilly but I guess it is my Scottishness showing through ;-)

However, what do you make of the near ground polygons with ice?

Hey, no need to apologise for hilly... I've many beloved memories of the times I spent up on Skye and in the Orkney and Shetland Islands, doing Outreach in the tiny schools up there... stood on a beach al Elgol, staring out across the water at the Cuilins glowing marmalade-orange at sunset and fell in love with the place...

I like the polygons... I think we're going to see some lovely ground features on Phoenix images. And, personally, I'm crossing my fingers that we see some beautiful atmospheric effects too... have always wanted to see a glowing halo around the Sun from Mars...

[Stu]

This is the best I've been able to make with Photoshop, a Gusev image and a "polygon" image...



Version 2 here and Version 3 here... which (if any!) will be more accurate do you think?

[SkyeLab]

Nice work Stu! I wonder if anyone else is going to have a bash at this?

I saw the competition being run from http://spaceurope.blogspot.com/ . Will you be entering?

Cheers

Brian

[Stu]

Nice work Stu! I wonder if anyone else is going to have a bash at this?

I saw the competition being run from http://spaceurope.blogspot.com/ . Will you be entering?

I can't... I'm a judge!

[SkyeLab]

How has the response been so far? A while to go yet I suppose though.......

[Stu]

How has the response been so far? A while to go yet I suppose though.......

Yep, a while yet, and you'd have to ask Rui how many entries there have been so far. We were kinda hoping there'd be some entrants from within the UMSF ranks (actually, there might have been, for all I know... )

Here's my latest "possible view..."

[ElkGroveDan]

Great image Stu, that definitely has a realistic appearance to it.

Alas even at this site there are still boulders to reckon with.

[Stu]

Great image Stu, that definitely has a realistic appearance to it.

Alas even at this site there are still boulders to reckon with.

Thanks Yeah, the boulders... just spent half an hour trying to add those realistically and got absolutely nowhere, so in MY world Phoenix lands in a remarkably boulder-free area!

[ElkGroveDan]

That's the right attitude!

[imipak]

in MY world Phoenix lands in a remarkably boulder-free area!

I like this "StuWorld", sounds like the place to be. I bet your Gusev is swept by regular windstorms too, right?

These images of terrestrial polygonal terrain posted above, and the HiRISE imagery, is not calming the gathering butterfly storm in my stomach. The boundaries of each 'hexagon' marks a point where frost heave has lifted thesurface of the inner area relative to the border areas (if I have my mental image of the process right?) So far as I can judge scale from Stu and Doug's simulations of Phoenix-by-HiRISE, there's a high probability that the lander will end up either straddling, or leaning down into, the 'ditches' around the polygons. I wonder what the maximum survivable tilt is.

Ah well, I suppose that lack of ground truth is what makes any Martian EDL so... "interesting"!

[Stu]

I must admit I'm struggling to make sense of the scale and nature of things at the Phoenix landing site... I'm going from pictures like these...



The top three images are terrestrial, the lower two crops from HiRISE landing ellipse image... I'm sure someone out there can give us a guide to what we're actually seeing on the HiRISE image..?

[ustrax]

Stu my friend...a pity you can't compete...why don't you use another identity?...
All the others...I'm still waiting for your entries...

[Phil Stooke]

Well, you got mine!

Phil

[ustrax]

Well, you got mine!

Phil

And a winner I must say...
Somehow I've got me this strong desire for a cup of good strong coffee...

[Phil Stooke]

Unfortunately I've been disqualified, so I'm posting mine here. Warning, it involves "flagrant digital plagiarism"

Phil

[ustrax]

Unfortunately I've been disqualified

Disqualified?!!
What do you mean by desqualified?!!
That was MY favourite so far...
Phil just didn't handled the pressure of being a favourite...

Just a a teaser for those who haven't sent participations yet, the prizes are being gathered this week at the US to cross the ocean on the upcoming week...these include the posters signed by Peter Smith and some of these beauties...

[Stu]

Unfortunately I've been disqualified, so I'm posting mine here. Warning, it involves "flagrant digital plagiarism"

Genius

The lawsuit is in the post, by the way.

BTW, some good Mars-related blog posts (including Emily's excellent piece on Mars Express images of Phobos) over at this week's Carnival of Space - the 50th!

[imipak]

Possibly of no relevance at all (and I know there are lot of other articles where the fulltext IS available), so just FWIW...:

http://www.jstor.org/pss/521255

..describes frost-heave polygons in Antartica "15 to 20m in diameter, and small frost mounds, 1-5m high".

15-20m sounds about right for the scale of some of the HiRISE images Stu's posted here (I think?) - I hope that doesn't imply 1-5m of vertical relief as well...

[ElkGroveDan]

OK I'm no Stu, but here's my attempt:

Attached thumbnail(s)

 

[ngunn]

These images are great fun - thanks all. I notice, though, that while terrestrial poygons tend to be light with dark outlines on Mars it seems to be the other way round. So far I don't see that reflected in the simulated views. And yes, I think they'd be pretty big - maybe only the nearest one or two clearly visible.

[SkyeLab]

OK,

Another effort.

Cheers

Brian

Attached thumbnail(s)

 

[centsworth_II]

I'm still waiting for your entries...

I just spent a lot of time working up an entry, but I've got two problems.

1) I'd love to show it in this thread, but since at least two of the judges
are here, I think that would be a disqualification.

2) I have never successfully sent a full resolution photo by e-mail,
but I guess I have time to figure that out.

[ustrax]

Why don't you hold on until the 24th of May to show it here, who knows, as a winner?

Dan...why didn't you send THAT great image?!
Come on...do me another version and e-mail it...
The same to all of you still thinking about it...get also the kids doing it, there's two categories!
Carla Bitter, Mission's Education & Public Outreach Manager, just e-mailed saying that the goodies were already shipped...

[ngunn]

Another effort.

Cheers

Brian

Excellent! - that one gets my vote.

I have to report that my attempt is making very slow progress. I've found some promising boulders and figured out how to work a digital camera, but I'm still trying to locate a dried up reservoir and someone willing to donate an industrial quantity of shaving foam . . .

[Stu]

OK,

Another effort.

Oooh, you might just have nailed it with that one Brian! Very nice.

I'm just worried we might see something like this when the first raw images come down...

[ngunn]

Or this:
http://images.google.co.uk/imgres?imgurl=h...l%3Den%26sa%3DG

[Juramike]

Or this:

[ustrax]

The goodies are already at Lisbon airport waiting for me to pick them up...
And Doug...are you ready for another Q'n'A?

[Stu]

Not long to go now...


WHAT WILL I SEE..?

The first time I open my sleep-heavy eyes
what alien landscape will curve around me?
A Barsoomian Narnia, with petrified fields
of snow-capped rocks and lonely frost-cracked
boulders, standing boldly beneath the glaring arctic Sun
like shrunken Easter Island statues?
Or will there be no stones to see, just an endless plain
of pale polygons stretching like a crumpled quilt
to the horizon, each icy lily pad a stepping stone
leading my startled eyes to a sky higher and wider
than any ever seen on Mars before..?

I wonder… will that sky be white – a mirror of Old Earth’s
bright Antarctic heaven? – or will it shine with a polished
metal hue, a cathedral-ceiling dome of brittle silver-blue
dwarfing every ridge and rock and stone cupped
in Green Valley’s gentle hands? Perhaps the frigid land
chosen to be my frozen tomb will stand silent
beneath a sea of blushing, perfect pink? Whichever
colour wins, will I witness wind-teased, lacy clouds
racing overhead, chasing each other like children at play,
mocking me with their faerie grace and speed
while I stare up at them helplessly;
my clumsy, manhole cover feet rooted to the frozen ground
as if I were a tree and they were birds?

Around the shrunken Sun I imagine a ring
of hoarfrost-on-Holly fire;
a perfect circle of Mother of Pearl light,
the crowning glory of the first
arctic martian sunset ever seen by Man.
On either side: a soft-edged slice of rainbow;
known as “sundogs” on Old Earth
the first Barsoomians shall call them
“Deja” and “fair Thuvia” in tribute
to the martian maids who stole John
Carter’s heart with just a sigh. And close by,
perhaps, an azure spark – Earth,
glinting as a sapphire gleams
when held up to the Moon until, too soon,
she drops into the burning dusk,
her flickering flame snuffed out…

And when my metal monkey paw claws at the
ground beneath my feet, what sight will greet
me as its dust and dirt are wrenched
and torn apart? Within that long-awaited trench
will my eyes spy only lines of old Noachian ice
or layers of “Can it be..?” green? Will My Mars be
as dead as the burial plains of Sagan’s hero Vikings,
or will my graphs whisper “There is Life here…”?

Soon I will know; soon my eyes
will open on a breathtaking new world,
and though no flag will I unfurl
to flutter and fly o’er Green Valley’s
frigid floor, on Landing Day I’ll stake a claim for
All Mankind, declaring in bold Shakespearean tones:
“We shall know no rest ‘til we have found Life here!”
and slowly, but surely, I'll play my role in that great Quest.

© Stuart Atkinson 2008

[ustrax]

And when my metal monkey paw claws at the
ground beneath my feet, what sight will greet
me as its dust and dirt are wrenched
and torn apart?

Here you have it...


Great poem my friend...the palms of my hands are getting all sweaty...
Terrible...just terrible!

[antipode]

Beautiful Stuart! I shivered while reading that - in a good way.

My aesthetic hopes for the mission

1) At least a little relief on the horizon (possible if it doesnt drill the landing ellipse?)
2) Atmospheric halo action (already mentioned)

and especially

3) The lander survives long enough to see the polar hood start to form and CO2 snow start to fall all around. Will it fall from a cloudy or clear sky? Will it only settle at night?

P

[Stu]

Not a million percent accurate, and I fear that the dawn sky there will actually be too bright to see anything in it, but in theory this is what Phoenix could see before sunrise during its mission...



Edit: "Jupiter" on the bottom image is actually VENUS. Just haven't got time to change the graphic now - due at work in 5 mins and it's a 10 min walk...

[djellison]

before sunrise

It wont be setting for some time after landing. We're north of the martian arctic circle here

Doug

[ElkGroveDan]

due at work in 5 mins and it's a 10 min walk...

Some of us don't need to hear that.

[Stu]

It wont be setting for some time after landing. We're north of the martian arctic circle here

Doug

Oh... ok... that's just what STARRY NIGHT showed me... maybe my co-ordinates were out.

I'll get me coat.

[SpaceListener]

Phoenix's Landing site

What direction will Phoenix be landing on , from South East (236 E) to North West (232 E) or viceversa? I seems that maybe, up to know, no one know until up to few days before landing.

According to the output of the space simulator, now Phoenix is about ahead of Mars from the Sun side. Now Phoenix will be approaching very slow to it until on May 25 by 10:25 UTC, Phoenix will start to approach to Mars in the opposite direction to its flight path from Earth to Mars. At that moment, the flight path will turn aheading from Mars at about 71,180 km/h at 10:20 UTC and forwarding to Mars at 9,986 kph at 10:25 UTC. That is a drastic reduction speed according to Earth as reference point. By then, Phoenix will slowly start to increase its speed toward Mars from South West to North East (same direction to the Mars's orbit). The planned touchtdown on Mars would be around 23:25 UTC.

I tought it as strange since Phoenix won't ignite an rocket engine to lower the speed before approaching to Mars. Maybe, Phoenix will be flying from lower Mars' orbit plane. Due to Mars' gravity, it will pull Phoenix to change its direction from below orbit plane toward to Mars.

However. I am not 100% sure of what Ihave interpreted images samples of every 5 minutes from the JPL's tool and also the input information to this tool is still valid? (http://space.jpl.nasa.gov).

[djellison]

What would be the point in using fuel now? I'm not sure what you're proposing. The spacecraft will land from the left in that diagram.

This is one of the 'not obvious at first' things about flying to Mars. Current - Phoenix is nearly ahead, and flying slower than Mars. Using the Sun as a reference Atmospheric Entry will actually speed up Phoenix

Doug

[SpaceListener]

Thanks Doug for the answer.

What would be the point in using fuel now? I'm not sure what you're proposing.

Previously I tought that Phoenix will throttle the engines to reduce its speed during its approach to Mars but it is discarded.

By the way, I have found the info which states:

Phoenix won't use any thrusters for breaking its speed toward Mars instead Phoenix will probably use the thrusters for short duration during two TCMs which are scheduled to be performed within the last three days. Just before entry, flight path data is sent to Phoenix that is used by the onboard computers during the descent and landing to guide the spacecraft to its landing site.

Hence, it is evident, up to now, the flight path for landing is still unconfirmed.

[slinted]

The latest MARCI Weather Report mentions a dust storm blowing around the north pole last week. It's somewhat hard to see in the rotating globe movie, but I think the edge of that system may have obscured the Phoenix landing site before moving on. I've been trying to get a sense of what the daily weather will be like once Phoenix lands. Is this what we might expect for this time of year? Localized dust storms? Pole wide storms? Clouds? I haven't seen much mention of this elsewhere.

[elakdawalla]

Thanks for the reminder about that site, slinted; it's an excellent idea to be checking the weekly weather reports to try and figure out what Phoenix is going to encounter on its way in. The penultimate report has some general information on what happens near the pole when spring arrives:

For those of us living in the Northern hemisphere here on the Earth, many of the telltale signs of spring have finally arrived. The northern spring on Mars officially began in December 2007, and over the past few months, we've observed many uniquely martian springtime weather phenomena. A few common springtime observations include dust storm activity and water ice clouds near the seasonal north polar cap edge, clouds and dust activity in the southern mid-latitudes, and the early development of the aphelion cloud belt. The weather this past week included all three of these springtime phenomena, with localized dust storm activity west of Argyre and in north Tempe near the seasonal north polar cap edge. Water ice clouds also persisted over the Tharsis volcanoes, with a notable "split" cloud at Ascraeus Mons, and mid-afternoon cloud formation centers apparent near the summits of Olympus and Arsia Mons.

--Emily

[dmuller]

When Phoenix meets Mars, the spacecraft will have a lower orbital speed around the Sun than Mars. Why? because the Phoenix orbit would take it all the way back to where it came from ... Earth (though Earth wouldnt be there at that particular time). So, in theory, Phoenix would have to speed up to match Mars' orbital speed and "stay" with it.

BUT

Phoenix (or any other craft going there) will get very close to Mars, and you want to stay there (land or orbit). So you cant fly "along" Mars because it's gravity would pull you in if you just match its orbital speed at close distance. The issue now is that you are too fast for Mars to capture you in its orbit, or land at a decent speed, so you have to slow down your orbital speed around MARS (not the Sun). Close to Mars, the gravitational force of Mars exceeds that of the Sun anyway, so you dont really care whether your orbital speed around the Sun goes up and down as you enter an orbit around Mars or land on it (it's a whole different story though if you use Mars for a swing-by).

Phoenix will reach the point from where the gravitational force to Mars exceeds the one to the Sun on 25-May-2008 11:25am SCET UTC, 12 hours before landing, at a distance from Mars of about 139,000 km

Phoenix will slow down its orbital speed around Mars as follows:
1. friction (glowing as it streaks through the atmosphere)
2. parachute
3. retro rockets for the last 500m or so only
4. ground impact

The remaining engine firings, TCMs, are not meant to slow the craft down to Mars, only to make sure it hits the atmosphere where it is supposed to.

Phoenix landing times are as follows:
Entry interface expected on 25 May 2008 23:31:12 UTC, landing expected on 25 May 2008 23:38:32 UTC Spacecraft event time
Entry interface expected on 25 May 2008 23:46:32 UTC, landing expected on 25 May 2008 23:53:52 UTC Earth received time

[Stu]

We REALLY don't want to come down in the middle of this lot, do we..?

[ElkGroveDan]

Unless we were to land just below that ridge right on top of that little crack that runs along the base of it.

[SpaceListener]

We REALLY don't want to come down in the middle of this lot, do we..?

Stu, I don't have the idea about the sizes of the stones. It can be interpreted as 1 cm or 1 meter since this picture has no referential size.

It would be very pity if the spacecraft loose the balance after the touchdown. The case landing MER is safer than the ones of Phoenix / Viking way of landing. This is because the ball will most probably be stopped whenever the surface is on the flat. Hope that MSL won't take so much risks as Phoenix does since MSL will cost many times more than Phoenix.

[nprev]

Oh, good Lord, no!!!! (SL, I'm gonna bet that those boulders are <1m each, since I think that the maximum resolution of HiRISE is 0.25m).

Sure looks like frost upheaval at work there, churning up the substrate; hopefully, it's very localized, and well away from the landing site. Scary as all hell, though.

[dmuller]

Someone asked whether Phoenix will land heading NW (diagonally up) or SE (diagonally down) on the landing ellipse. I assumed the formed but after some research seem to have been wrong! Here's the reasoning I figured out and gave that person, but did I miss something?:

Mars, on 25 May, is about 7.4 million km above the eclipitc. Phoenix, when it launched, was right on it (by definition). So at the moment it is approaching Mars from the South, will cross it's equator and head North. Mars' gravity will pull it back South just a little. So it will land from the North West and head South East (from higher to lower) in the landing elipse. Compare the following 3 images (load them, then use back / forward in your browser):

http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1
http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1
http://space.jpl.nasa.gov/cgi-bin/wspace?t...=1&showsc=1

That's Mars seen from above (in 1 minute intervals), and you can see Phoenix heading "down" again as it starts descending through the atmosphere
That's what I can figure out, at least

[infocat13]

[quote name='dmuller' date='Apr 26 2008, 04:44 PM' post='112865']
Someone asked whether Phoenix will land heading NW (diagonally up) or SE (diagonally down) on the landing ellipse. I assumed the formed but after some research seem to have been wrong! Here's the reasoning I figured out and gave that person, but did I miss something?:


what we need is a friendly JPL mission design or better yet aerodynamics folks to give us a glimpse of some of the AIAA aerodynamics papers on Phoenix.Unfortunately AIAA is very jealous about its copyright even through all of there papers are stamped
"paid by nasa grant number........"

This is a prelaunch astrodynamics/mission design paper for Phoenix scroll down to page 14 and are good images of approach and entry geometry.

http://trs-new.jpl.nasa.gov/dspace/bitstre...1/1/07-0267.pdf

[Stu]

Stu, I don't have the idea about the sizes of the stones. It can be interpreted as 1 cm or 1 meter since this picture has no referential size.

Wow, if HiRISE can suddenly spot rocks 1cm across it's had a heck of an upgrade!

As HiRISE's best resolution is typically - correct me if I'm wrong, someone - "around a metre" then those rocks are each bigger than Phoenix. Again, I stand ready to be corrected here guys...

... but I'm going to have nightmares about "The Hump Of Horror" on PSP_002104_2485...!!!









Having said that, imagine the view if Phoenix lands smack bang in the middle of that Hump... so much for "few rocks and boulders visible..."

Actually, being serious for a moment, why would these be so many rocks here and not elsewhere in this region? Why have they collected - or gathered - around the edge of this feature? There's another similar mound further "down" the strip, and it too has rocks arranged around its edge. What gives..?

[dvandorn]

As HiRISE's best resolution is typically - correct me if I'm wrong, someone - "around a metre" then those rocks are each bigger than Phoenix. Again, I stand ready to be corrected here guys...

HiRISE's best resolution is actually roughly 30cm (or very roughly one foot, for those of us who still use Imperial units). That said, though, I'd think you're still correct, each of those rocks is likely as larger as, or larger than, Phoenix itself.

-the other Doug

[dmuller]

This is a prelaunch astrodynamics/mission design paper for Phoenix scroll down to page 14 and are good images of approach and entry geometry.

Thanks infocat ... I used that document, and duly cited it, for some of the information used on my real-time Phoenix simulation script. Slipped my mind to look at it again to answer that question. Looks to me like we are going with "Page 14, Figure 13 EDL Communications Geometry, Open Launch" as shown in that document.

But yes it is a premission document, some things changed quite a bit. More information would definitively be a great plus. Emily mentioned the script on her Planetary Organization Blog, and I've had 250 site views on Saturday alone.

Daniel

[edstrick]

"...in the middle of this lot..."

It would be perfectly nice if it came down in the MIDDLE... between boulders.... ON TOP OF... that's different!

Another lower probability nightmare is if it came down nicely on a nice BIG flat-rock.... nice and level and undamaged... and with the sample scoop able to reach down to 1 centimeter ABOVE the ground below the edge of the rock. aaaAAAAUUURRGGGG!

[djellison]

It lands W to E because, looking at Mars, it flys left to right. Once you figure that Phoenix is ahead of Mars, then the geometry becomes self evident to be honest.

Doug

[Stu]

Hmmm... this could be interesting, or it might be nothing.

Was perusing the images listed in Emily's Blog posting re HiRISE images of the landing site, and whilst wandering over PSP_006785_2485 I found this...



... and the colour version of a neighbouring area looks like this...



Anyone else think they look like the "geyser"-type features seen down near the south pole..? Could Phoenix land near... no, that would be too much to ask for, wouldn't it..?

[ElkGroveDan]

Good eye Stu.

Imagine images of a geyser plume on the horizon. Maybe it's not too late to add one to Rui's contest...

[djellison]

I'd have thought they'd happen during the spring, when the place is warming up and the ice retreating. Phoenix is arriving when all the action, I'd have thought, would be over

Doug

[Stu]

I'd have thought they'd happen during the spring, when the place is warming up and the ice retreating. Phoenix is arriving when all the action, I'd have thought, would be over

Doug

I thought that too... but there could be some interesting material on the surface, and reachable with the instruments, if Phoenix were to land close to one of these vents, even if it's inactive...

[ElkGroveDan]

OK fine. No picture then. I remember when folks around here had vision and imagination

I may do the picture anyway.

[nprev]

Aah, c'mon. Dan...they do.

Speaking as one of the judges for Rui's contest, would love to see a geyser on the horizon in one of the entries (because, frankly, who the hell knows? We don't have a bleeding clue about the rate of thermal inertia for the terrain, fooling ourselves if we think so, even more so if we assume it's uniform...)

[SpaceListener]

Stu, 1 cm, impossible, then closer to 1 meter is the most likely. Thanks to Nep, Stu and The other Doug.

The other thing, about after interpreting the picture, what I was thinking that the surface must be somewhat wet (ending the spring and some water might have sublimated?? and the other part might have drought into the surface??). The surface aspect is smooth probably by the ice weight and by the water erosion and the surface have no white color, then no snow??. This contradicts to Planetary blog (Phoenix on Course for Mars Landing) which says that the zone landing surface will be covered by ice.

"Our landing area has the largest concentration of ice on Mars outside of the polar caps. If you want to search for a habitable zone in the arctic permafrost, then this is the place to go," said Peter Smith, principal investigator for the mission, at the University of Arizona, Tucson.

Finally, I am preoccupied about the success of landing since the ellipse landing is so big (the landing area is an ellipse about 100 kilometers (62 miles) by 19 kilometers (12 miles)). Indeed, according to the Phonix Web page says:

the sophisticated landing system on Phoenix allows the spacecraft to touch down within 10 km (6.2 miles) of the targeted landing area.

On the other hand, I have heard that the intelligent discrimination among boulders was deactivated in order to avoid a major complication in deciding rightly the landing site. Although I have found a quote from Phoenix's Arizona's Web which says:

Besides, the Phoenix's navigation system is capable of detecting and avoiding hazards on the surface of Mars.

[djellison]

I was thinking that the surface must be somewhat wet

What makes you think that? The temperatures and pressures involved render liquid water a very very transient phenomenon, with sublimation far and away the dominant process.

And the resolution is not a 'more likely' situation - it's not an interpretive issue. Each pixel IS 25cm.

The blog doesn't say it'll be covered with ice. It say there is ice there. Which there is - in the soil. Not on it. In it.

I think the two articles you've seen citing landing accuracy are out of date. An active, guided entry was an initial plan for Phoenix, but it was cancelled to save money.

Doug

[ustrax]

Maybe it's not too late to add one to Rui's contest...

Well...there's only 20 days left...and I already have the prizes with me...
those signed posters are indeed a beauty...
I'll try to post an image from one of them already in place at spacEurope's HQ

EDITED: Signed posters, pretty t-shirts and 15 days to go...