And despite what the various hoax believers say, we have landed many craft on the Moon. (Some of them with humans inside!) I've never heard of any of the "anomalies" that Jerry constantly cites for landings on bodies with atmospheres.

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Microsoft is over if you want it.

The bar has been lowered for the promotion of ATM ideas; the bar for the acceptance of ATM ideas must remain high.

More of a very, very, very slow crash!

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

Check out this thread - primarily the first post:

Mars: Hard to hit, or are Probes hitting too hard?

I think a trend can be glumed from the data: Things fall faster through the atmosphere of Mars than we expect them to. A couple of carefully monitored landings on moons or planets that are not near the Earth's orbit could prove definitive. (I think the gravitational data Messenger sorts out from Mercury will provide a lot of answers as well, but then I though Cassini would have the whole issue decided by now.)

As the gravity B probe scientist learned, gravity is very illusive to nail down. Near the Earth we have the major tidal swings to deal with, and the elasticity of both the Earth and Moon - even the rain in a thunderstorm can bias a careful gravity experiment.

We can't test gravity at the smallest non-relative scales, we can't tell whether galatic rotations are driven by Dark Matter, MOND or any other theory that decouples inertia from gravity. Well we can - that is what the Pioneer probes are - we just don't know how to interprete what we are seeing.

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jwj

It's ok not to know. We should try harder to find out.

How could Phoenix have landed any better? You are going to have to realy grasp to get anythging out of this one.

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'The eye can only see what the mind is prepared to accept'

Phoenix was right in the crosshairs of MRO during the parachute descent, meaning the entry was very close to exactly on-targert. The parachute and heat shield landed very close to the Phoenix, meaning there was little wind near the surface. Perfect Perfect Perfect. Three sigma from the center of the targeted landing area. How could that be?

As I said above, if the lower atmosphere is more dense, and the upper atmosphere less dense than calculated, MRO would catch the parachute deployment (even though it was late - due to the less dense upper atmosphere) but during the slower descent at lower altitude, the residual horizonal momentum from the time-of-entry will drift the probe to the edge of the target area at a higher relative rate than if the lower atmosphere is at the predicted density - remember the wind velocities, based upon the capture of the descent by MRO and the close proximity of the ejected parachute are likely quite low. One possible answer.

A greater-atmospheric-gradient-than-expected could be a chance effect; but if you looked at the prior Mars landing data I provided a link to, you will find every successful entry has a similar pattern of late parachute deployment and unmodeled forces near the surface. (Pathfinder reconstuction ends with a dotted line, indicating they could not model the final segment, likewise analysts gave up when they tried to model both Viking probe final approach fuel consumption.)

The jury is still out: When NASA was ask why the probe was on the fringe of the target area, the response was, they were still analysing that. Don't expect an answer very soon: The less-well something is understood, the longer the science team will ponder the results before reaching any conclusions. No one likes to admit they are stumped. (It was ~ decade before the Pioneer anomally was made public, and the anomalous acceleration during Earth flyby's was first observe a decade before it was published by Anderson et al.) The Gravity Probe B team just ask for a third extension to study their data. Have you ever read the press release that said Spirit was within seconds of getting smushed? It was. No one is hiding anything - They just want to understand the data before they publish. So do I.

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jwj

It's ok not to know. We should try harder to find out.

Man, Jerry, you are a real piece of work!

Before the event, you said "let's see where it lands".

Bull's eye!

Now, you're saying "B-b-b-but, it didn't hit the exact middle of the landing ellipse."

News flash!
If they had known exactly where it was going to land, they wouldn't need an ellipse!

I'm not even going to touch your "if we fudge the atmosphere parameters, I could still be right" argument!

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

It missed the three sigma ellipse, or was on the very edge. Three sigma means 99.9+ confidence, allowing for All known sources of error. All probes land within 0.1% of expectations. It was a fairly large Ellipse, allowing for winds, entry angle and known ballistic variances, and recalculated within days of the actual entry. Phoenix was exactly on target at the point of entry. At the present time, there is no reason to suspect wind velocities were beyond three sigma expections.

http://planetary.org/blog/article/00001461/

It reminds me of a screwball pitcher. Everyone knows the pitch is near the plate, but not even the catcher knows what will happen in the final three meters. We do much better when landing on the Earth - we can extrapolate from the velocity, attitude and point of entry to the final landing point, and unless the winds are more than three sigma from expectations, neither is the landing. The winds were not three sigma beyond expections on Mars, why was the probe? It is PREMATURE to speculate until the project team has made an assessment. What I said was, don't expect an answer soon, because I don't think they can explain it using known physics.

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jwj

It's ok not to know. We should try harder to find out.

B.S.

Bull's eye is generally regarded to be well within ONE sigma. Three sigma is absolutely everything we are not in control of being at the fringe of our expectations...99% of the time we will be within three sigma. That means hitting the dart board after nine shots of hard liquor (for me).

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jwj

It's ok not to know. We should try harder to find out.

Who is this Jury that is still out?

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'The eye can only see what the mind is prepared to accept'

The jury went home long ago!

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

Right now, the project EDL (Entry Descent and Landing) team is trying to piece together how Phoenix got from point 'A' to point 'B'. If the laws of physics do not need to be changed, they should be able to do this with reasonable assumptions about atmospheric pressure and winds, and in a reasonable amount of time.

The other curious thing about the entry is that there was no plasma black-out during entry. This has happened on Mars before. It may mean nothing, but it is a little inconsistent with our experience during entries on earth.

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jwj

It's ok not to know. We should try harder to find out.

AFAIK there are no plasma blackouts during Shuttle re-entries. There were blackouts during earlier space missions, but back then communications did not use communication satellites.

It is a function of the peak dynamic loading during entry - the Shuttle is in low earth orbit - just barely above atmospheric minimums. The Apollo Moon Probes came racing in at much greater velocities.

The pressure on the Phoenix heat shield should have generated enough heat to induce a brief plasma blackout. Since it did not, the only gap in the doppler signature should be during antenna change over - about seven seconds fairly close to landing. The mission scientists should be able to put together a complete picture.

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jwj

It's ok not to know. We should try harder to find out.

This NASA document seems to indicate that even the smaller Mercury and Gemini missions typically encountered LOS during re-entry. Surely most of their re-entry speeds were similar (or lower) to the Shuttle's, with respect to the Apollo trans-lunar re-entry speeds. If I misunderstand the topic here I'm ready to stand corrected.

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"Ignorance more frequently begets confidence than does knowledge" -- Charles Darwin
"Ignorance convinces" -- slang's dad
"Your right to hold an opinion is not being contested. Your expectation that it be taken seriously is." -- Jason Thompson

No, you are correct. It is not as simple as I said, there are a few other factors I am aware of. The capsules use ablatived heat shields, and pass through the atmosphere rather quickly. The shuttle is a winged entry that uses insulated tiles rather than an ablative heat shield. As a winged craft, the shuttles angle-of-attack is much shallower, spending many more minutes in the atmospheric descent. Finally, the craft itself has a much greater surface area, so even when the gases passing over the shuttle are very hot, there is a much wider corridor for radio signals from above to be transmitted to-and-from the aircraft.

In any case, the Phoenix mission engineers expected enough plasma to disrupt transmissions. I think (but I am not certain) both Spirit and Opportunity also failed to realize expected transmission blackouts. There was great interest expressed by the Discovery Mission EDL team at the time Opportunity photographed her heat shield, but I am not aware of any published reports of their study and conclusions about either the heat shield, or Spirits late parachute deployment.

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jwj

It's ok not to know. We should try harder to find out.

During the early days, many attempted to explain the earth-centered working of the solar system, logically. None of the explanations stood the test of time. Then Kepler gave seemingly-scientific basis to the sun-centered model of the solar system. Although this was more logical, it assumed a static central body and a solar system as viewed by an observer on the sun or outside the solar system. There was no idea of gravity or the central force, until Newton produced his theories. Newton’s theories tried to give logical reasons to Kepler’s laws and in turn, produced proofs for his theories on gravity and laws of forces. His theories were proved on the basis of Kepler’s ideas on the apparent orbital motions of the planets around the static body of the sun. Now we know that the Sun is not a static body in space. However, the notion of planets of solar system, orbiting around the sun is still preserved by the scientific community. Earth, orbiting around the sun is like a person trying to walk around a running bus. It is an impossibility. Only possible path of the walker is to move in a zigzag path about the path of the bus at nearly at the same speed (cyclically varying within small margin) as that of the bus. Same is the case about all planets in a multi-body system.

You seem to be a little behind the times, matterdoc. How do you know the bus is moving? Of course, that's simple: it's moving relative to the ground. But when you get out into space, where is the ground? There is no ground! Not only that, there is no 'static' ether by which to compare all other movement, and there is no preferred reference frame. Einstein, 1905. If you drop an object as you are bicycling along, does the object drop "straight" down? No! It retains the forward velocity you had when you dropped it. Same with the planets and the Sun.

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Everyone is entitled to his own opinion, but not his own facts.

This is true without relativity; and what it proves is that either gravity is instantanious, or a vector quantity. An eather has not been totally disproven. What has been proven that an eather, a wave property of space, that is independant of the motion of the earth does not exist. Although this issue seemed settled decades ago, there are many reasons that eyebrows are rising today. We find several parallels to the search for an eather in today's astrophysics: The absence of detectable gravitational waves, gravitational particles and whimps. We have to keep looking.

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jwj

It's ok not to know. We should try harder to find out.

Walker can judge his motion with respect to the bus. That is how, a planet is judged in its orbital path - with respect to the Sun. Whether there is an absolute reference or not, their relative displacements will indicat