[X] My Assistant

[ustrax]

Doug, you took my expression too literally...I was referring more to that 5am press conference, which by the way Stu...isn't it on Monday morning, working day already?...

[centsworth_II]

...isn't it on Monday morning, working day already?...

Don't tell me I'm the only one that plans vacation days
from work around significant space exploration events.

Great interview by Stu on your blog, ustrax. I think I'll
let the folks over at the space.com Phoenix thread know about it.

[ustrax]

Don't tell me I'm the only one that plans vacation days
from work around significant space exploration events.

Great interview by Stu on your blog, ustrax. I think I'll
let the folks over at the space.com Phoenix thread know about it.

I think I'll arrive the office sooner than usual...
If it were a month earlier it would be the perfect long weekend...

Yes, Stu made a splendid job! ustrax just loves his crewmates...

And don't forget to participate in the competition!

[jamescanvin]

Don't tell me I'm the only one that plans vacation days
from work around significant space exploration events.

I'm probably going to take the Monday off, I wouldn't get any work done even if I did go in.

[djellison]

It's the Spring Bank Holiday Monday James WIN

Doug

[Stu]

which by the way Stu...isn't it on Monday morning, working day already?...

It would be if it was the previous or following Monday, but because of my bizarre work rotas this Monday falls on my beloved "3 day weekend"... To quote a quaint old English phrase, GET IN THERE!!!

[SpaceListener]

Now it is 45 days away from landing on Mars. As the Phoenix spacecraft will be approaching to Mars at the 120,000 km/h and Mars would be traveling around 96,600 km/h and the diferencial speed when Phoenix enters to Martian's atmosphere at around 23,400 km/h. However, this speed is of horizontal vector with respect to the Mars and Phoenix travel path. I don't know about how fast would be Phoenix be traveling around Mars with respect to Mars's orbital speed.

Well, now, I still haven't found any details about the landing Phoenix path on Mars.

I am supossing that Mars is orbiting in counter-clockwise. On the other hand, Phoenix will be a little behind of Mars until the the Phoenix with its greater speed pick up the Mars on the top of the atmosphere. As the spacecraft was approaching very slow to Mars and hence will be traveling in clockwise around Mars.

The question is: How long will Phoenix be traveling around Mars until its touch down at 68 North and 233 Longitudinal East at 7:36pm Eastern Daylight Time?

Then we are going to be holding the cross fingers for others 17 minutes until knowing its first signal beeps!!!

P.D. Corrected the speed (km/s -> km/h) thanks to Ugordan!

[ugordan]

As the Phoenix spacecraft will be approaching to Mars at the 120,000 km/s and Mars would be traveling around 96,600 km/s and the diferencial speed when Phoenix enters to Martian's atmosphere at around 23,400 km/s.

I believe you're thinking in km/h and not km/s there. At least I hope you are, I don't think there are many spacecraft that can stand that kind of heating and deceleration...

[dmuller]

I believe it's more of a "straight-in-and-down" approach, not much orbiting around Mars. The last trajectory maneuver 22 hours before landing will be at about 230,000 km, 10 times as far away as the Deimos orbit. At that time, the gravitational acceleration to the sun is still greater than that to Mars (barring any errors in my algebra)! At the moment, Phoenix is 9.7 million kms above Mars, but still has 81 million kms to go. According to the Phoenix website, its speed at Entry Interface (first contact with the Martian atmosphere, is 5.7 km/sec

[edstrick]

Cruise, terminal approach, jettison of the cruise stage, and entry will be essentially similar to MER, MSL, Polar Lander and Pathfinder. Details will differ, such as: no relay communications from Polar Lander after it turned away from telemetry-to-earth attitude, etc. But till the hypervelocity meteoric phase of entry is over, it's only details, not the essence of what's happened.

Following parachute deployment, once the bottom of the aeroshell is jettisoned, it's no longer "details" that are different.

[Stu]

Congratulations to Rui for organising this evening's enlightening and informative "Live Q&A" with Peter Smith. Several UMSFers took part, and Peter answered as many questions as he could in the limited time he had available. You can read the Q&A here.

[Stu]

For those people who haven't yet taken a look (shame on you! ) at Rui's excellent Q&A from yesterday with Peter Smith over on the spacEurope blog, here are some snippets... some real gold nuggets of info in here...

The robotic arm is 2.35 m long and powerful enough to scrape into hard
materials. It is true that if the spacecraft footpad perches on a rock or is
otherwise unstable, then the RA has the strength to move the lander. We often
joke that landing on ice in low gravity will allow us to pull ourselves along
the surface using the RA from rock to rock. If the ice is exceptionally hard
we will not dig through it, but instead, will use our RASP to scrape up
samples to be delivered to instruments on our deck.

The MARDI instrument was found to interfere with the guidance system under
rare circumstances forcing the difficult decision to turn it off during the
descent. The microphone does work and may be used later in the mission to hear
the sounds of the RA scraping on the Martian ice.

Discovering Martian life is beyond the goal of this mission. We are looking
first to see if the Martian arctic is habitable: periodic liquid water,
organic material (it could be from meteors), and energy sources available for
power an organism.

On May 25, the lander "feels" the Martian gravity and begins to accelerate
toward the planet. Its speed increases from 6000 to 12,500 mph. Fifteen
minutes before entry, the lander separates from the cruise stage that have
been its life support system for the last 10 months since launch. Seven
minutes before landing, we enter the upper atmosphere and the aeroshell
experiences the heat of friction with the thin atmosphere. We must enter
within a degree of our proper angle or else we can skip off into space or heat
too rapidly and overwhelm our protection systems.

After the aeroshell has slowed us to 900 mph, the parachute is deployed and we
start a leisurely descent to about 1 km above the surface. At a speed of 150
mph, the spacecraft is released from the backshell and drops toward the
surface. Twelve thruster ignite and using radar for guidance bring us to our
landing site at a speed of 5 mph. the specially designed landing legs take up
the shock of landing. Fifteen minutes later the solar arrays deploy and the
camera starts taking images. Our mission begins.

The first week of the mission consists of taking images and preparing for
gathering samples. At the end of the first week we expect to have delivered a
surface sample to our TEGA instrument. The summer is our prime science
opportunity and we expect to meet all our mission goals by September. As you
might expect, the mission will continue longer than this up until solar
conjunction in mid-November. Recovering operations after that in late December
will be very difficult as the Sun is setting in this high arctic region. By
February we expect that carbon dioxide ice is forming a thick layer around the
lander and without heat Phoenix will not survive. No 4 year mission for us.

The landing site has been well imaged from space by the HiRISE camera, a 0.5 m
telescope with resolution of rocks 1 - 1.5 m or greater. We have found a safe
site with few boulders to insure a safe landing. However, it will not be free
of cobbles and smaller pebbles. I am curious to see how these stones have
weathered over time and whether they are aligned with the polygonal
boundaries.

There are few slopes in the neighborhood and the horizon should look extremely
flat, no hills. However, the site is far from boring. We are near a 10 km
crater and should be on the ejecta blanket containing material brought to the
surface from depth. We are also on the slope of a large volcano, Alba Patera
and may encounter ash blown from the interior. Finally, the site is a shallow
valley and has undergone erosion which may leave signatures.

We land just before summer solstice and the first few months of the mission
have plenty of sunlight altho our power generation depends on the tilt of the
lander which we cannot control. Our science team has many arguments about how
ice might react when the overburden of soil is removed. We will try to force
some of the ice to melt by putting it in the warmest place we can find--the
lander deck, then imaging it as solar heating tries to melt it. The question
is will it sublimate before melting?

We are flying an atomic force microscope built in Switzerland by Urs Staufer
for the first time ever. This is a difficult instrument to fly because it is
sensitive to vibration even the tiny vibes caused by temperature change and
wind. It has worked well in the lab and during environmental tests giving a
resolution of an amazing 100 nm per pixel.

Our TEGA instrument which has 8 ovens is used to determine the minerals in the
soil and to drive off vapors which are measured in a mass spectrometer. The
ovens can only be used once so we must allocate them intelligently. Our basic
goal is a surface measurement, an ice sample, and a sample half way between.
Then will try to verify that what we have seen is real if the signal are near
the noise level.

Our thruster use hydrazine as fuel, its formula is N2H4 and our ultra-pure
mixture has no detectable organics. The combustion products are ammonia and
water. The more difficult question is what about the 1% that doesn't combust,
it is highly reactive and may alter the chemistry of the surface layers that
it contacts. We are vigilant and will try to avoid contaminated areas.

Another major part of our science is the study of polar climate. Not only is
Phoenix a traditional weather station, but we use LIDAR, built by our Canadian
partners, to measure cloud properties and heights. The camera has special
lenses for determining dust opacity and we do look for atmospheric phenomena
like dust devils and solar haloes.

The end of the mission has not been carefully studied and there are no
guarantees after we complete our primary mission. As much as anything, the
NASA budget limits our longevity. We will do everything in our power to last
until the last rays of sunlight energize the spacecraft.

All good things come to an end and we will leave important questions for
future mission to unravel--Phoenix is a stepping stone on the path to
discovering the Truth about Mars.

Good bye all and thank you for your interest!

[AndyG]

The answers and info were good, Stu - but:

"The microphone does work and may be used later in the mission to hear
the sounds of the RA scraping on the Martian ice."

"May"? I can't think of anything more wonderful, both in terms of your sort of outreach work and for the sheer coolness factor, of sounds from Mars.

Andy

[nprev]

Quick question, if anybody knows: Does Phoenix have an inertial measurement unit (IMU) on the spacecraft bus itself, or is this or an analogous device installed on the EDL hardware?

Sneaky idea here: IF there's an IMU on Phoenix itself (there has to be some sort of three-axis rate sensor suite for terminal descent, anyhow; FOGs or something?), and IF it could be spun up again post-landing within the power budget, and IF the meteorology data is of sufficient resolution, THEN we have a poor man's seismometer. The IMU/rate sensor suite wouldn't really need to align to any particular direction or orientation as long as the stable platform can be aligned at all with some axial offset along all three; we could measure three-axis acceleration vectors regardless & subtract the angular effects from 0.38g at any given orientation. The met data would be used to distinguish between wind effects vs. actual shakes & quakes.

Okay, ready to hear that I've reinvented the wheel yet again, but made it square this time...

[nprev]

On another topic, our own ustrax has scored yet another journalistic coup on spacEurope: some words from the director of JPL on Phoenix!