[9:39 pm]
Greg: For me, one of the most astounding things about space exploration has been how NASA engineers evolved the idea of speed. They have developed such powerful thrusters for these space crafts and I don't think regular citizens realize how much power these things are packing. Below is an estimated speed chart of the Phoenix Lander...pretty amazing.

[9:27 pm]
Greg: What did we learn from the failure of the last Mars Polar Lander? How is this mission different? What's been changed about the lander to ensure success?

Robert: We learned a lot from Mars Polar Lander. First we learned that MPL was basically a sound design. This lander looks a lot like MPL. That is one reason this mission is a economical as it is. We have leveraged hugely off the MPL design, much of it implemented for the Mars 2001project that was ultimately canceled.

We spent a great deal of time and effort to understand what went wrong on MPL Landing day, and have taken great steps to make sure we don't fall victim to the same problems. Additionally, we modified the communication scheme used during our Landing to make sure that the operations team on Earth has a clear understanding of what is going on with the Lander at every step along the way.

We also learned a bit of humility from Mars Polar Lander. You have heard the cliche "Well, it ain't rocket science..." Well, this IS rocket science. Building a system and sending it far far away from home, and expecting it to deal with every challenge it meets, carries non-trivial risk. There are "unknown" elements in a venture like this. That is a big part of why we are going! This is science. We have tried to limit those unknown elements, and have applied all the wisdom
we can from the experiences to date.

[9:19 pm]
Greg: What are our next steps for Mars?

Robert: The next mission slated for Mars is called Mars Science Laboratory. It is a much larger Rover than Spirit and Opportunity, about the size of a small SUV. It will be powered by a small portable nuclear power source that it will carry around with it instead of depending on Solar Arrays to gather sun-light. This will both stretch its mission, and allow it more freedom of operations than the MER rovers had. It is planned to launch in 2009.

[9:12 pm]
Greg: For me it seems like time has stopped as I wait on edge for the first images to be sent back. What are most of the personnel at each center doing right now? Are there any clear diagnostics that can be analyzed already or is still to soon to be getting data back from the lander?

Robert: Well, I am listening to that post-edl poll. All the stations are reporting that error counts were zero, trajectories looked nominal, the time line looks to have run a little long, but nothing outside the expected bounds.

As of one-minute past touchdown, every thing looks nominal. By the way, we expected to loose communication one minute past touchdown since that is when the Orbiters disappeared over the horizon. At this point we wait (patiently... HEY! I Said PATIENTLY!!) for the next overflight in about two hours.

[9:00 pm]
Greg: As we wait for the first images to come from the lander, how about a light hearted question? Do you believe humans will ever walk on Mars? Live on Mars?

Robert: Oh, now you are asking my opinion. I'll happily answer the question,
but realize that my answer is my opinion, not any NASA policy.

I grew up reading novels by Robert Heinlein, and others (which are still cool reading materials even today). I have this belief that the day will come when people are born, live full and productive lives, and die without ever setting foot on Mother Earth. Earth will be viewed as that place where the human race took root, but nobody actually goes there any more! In that world, grade school teachers will teach lessons about the quaint little robotically operated machines that people used to send to other planets to do geology studies. Now, lets all go outside and pick up a sample of sand so we can start our lab work.

I do not expect we will reach that point in my lifetime.

In the same way that we look back at the sea-farers of 400 years ago, who demonstrated that you could get to India without sailing around the tip of Africa, and oh-golly! there's another continent out there!

In the same way that 150 years ago traveling from St Louis to Los Angeles was a trip that few people made more than once because three months in a conestoga wagon was a life threatening experience, and not for the feint of heart. I believe that the ground-breaking science, and engineering feats that these Mars missions represent are only our first fumbling steps as we venture beyond this planet. We, the Human Race, are at the beginning of an amazing journey, and time alone will determine where we will reach.

Enjoy the ride!

[8:50 pm]
Greg: We just heard that there will be a "post touchdown poll", can you explain what that means to our viewers?

Robert: The post-touchdown poll means that the Mission Manager wants all the people in the Mission Support Area at JPL to look at the data concerning their discipline, and evaluate the health of the spacecraft. The thermal guys will look through all the temperature data. The Communication guys will look at signal strength recorded through EDL. The Navigation team will look at what information we have as to how close the Lander came to following the prescribed profile.

Then over the head-set network, he will aske each station in turn if they saw any anomalies that need further investigation. The first blush look at the data said everything looks good. He just wants a more thorough check.

[8:40 pm]
Greg: Well....the Lander has touched down, every team is gathering and doing further diagnostics. The lander on the other hand is doing a number of things. Below are two videos of what Robert, Miles and the rest of the engineers involved hope the lander is doing at this very moment.

[8:36 pm]
Matt: What kind of processes is the lander going through right now as it is sitting on Mars' North Pole?

Robert:The landed initialization sequence starts with 15 minutes of nothing. We want to allow any dust that we kicked up to settle. The next thing we do is drain the pressure from the propulsion system by venting the high-pressure helium tank. Then we open our Solar Arrays. These are like big Japanese fans on opposite sides of the Lander.

Once the Solar arrays are out, we will release the Camera mast which opens up like a Jack-in-the-box, and the Mast that supports our meteorological measurement sensors. Next we open the Bio-barrier that has been covering the Robotic Arm. The Bio-barrier had been keeping the Robotic Arm extremely clean all during the late phases of pre-launch operations. Now that we are on the surface we don't need that protection.

Once all the deployments are complete, we will take a bunch of pictures to verify that everything went well, and wait for the next orbiter pass.

... what could be simpler!!!

[8:24 pm]
Greg: What are our next steps for Mars?

Robert:The next mission slated for Mars is called Mars Science Laboratory. It is a much larger Rover than Spirit and Opportunity, about the size of a small SUV. It will be powered by a small portable nuclear power source that it will carry around with it instead of depending on Solar Arrays to gather sun-light. This will both stretch its mission, and allow it more freedom of operations than the MER rovers had. It is planned to launch in 2009.

[8:18 pm]
Linda asks: Wow, this has been interesting, I never actually paid this much attention to the landing of a mars probe. How many statisticians do you have on this mission (as a stat-woman myself, always curious where we find ourselves) - or do you have other engineers/scientists with stats knowledge?

Robert: Holy Mackerel! That is a huge question to try to answer in a Blog!

If you try to count everybody, you have to include the instrument teams, the science teams, the Spacecraft team in Denver, the Project team in Pasadena, along with the Navigation team. There is also the Deep Space Network with stations around the world, and the Odyssey, ane MRO teams that are helping relay signals back to earth. Oh, and the folks in Greenbank, WV that are listening for our UHF carrier signal. We are talking several thousand people here. Phoenix has many many proud parents right about now.

... and they all stand out!

[8:13 pm]
Greg: Another check in from Elspeth....

The Phoenix has landed! And everyone in mission control is celebrating! Some are laughing, some are crying, many are calling home with the news, and I got chills as I watched the celebration proceed. These people have spent so much time and energy and the landing could not have gone better. They had a direct connection with the Odyssey the whole time. They have been collecting data ever since it set down and all the signals are strong. The Lander is at only a quarter degree tilt so almost perfectly horizontal. The next big step is the deployment of the solar arrays which will confirm that the Lander is in good condition. Everyone is expecting to get the first pictures within an hour and a half!

[8:08 pm]
Greg: Signal seems to be getting stronger and that the landing is on course.
What is the mood like right now in the space operations center?

Miles: We are on the surface of Mars! Next step is to get the solar arrays deployed and start looking at the state of the lander and..... a first-ever look at the Martian polar region.

Robert: Electric! Lots of nerves in the room are a bit frayed. But you know what? One-way light time is a little more than 15 minutes. That means that EDL has actually already completed; one way or another. We are just patiently waiting to hear about it!

[8:04 pm]
Greg: Can you walk us through the landing of Phoenix? How fast is it moving when it reaches Mars Orbit? How does it slow down? How big is it's parachute? What temperatures will the heat shield face?

Robert: The sequence of actions we call EDL (which stands for Entry, Descent, and Landing) all take place in less than 10 minutes. In that time the Lander will decellerate from over 5500 meters/sec (over 12000 mph) to stationary on the surface. Most of that slowing down happens due to the friction with the atmosphere. (Remember that the Martian atmosphere is one one-hundreth the denisity of Earth atmosphere.) We come in on a flight path that is almost parallel to the ground and allow the air to slow us down. We have a heat shield made of a special cork-like material that protects the lander from the intense heat. The surface of the heat shield will reach temperatures nearly as hot as the surface of the Sun.

Once we slow down to about 300 m/s (about 650 mph), we will deploy a parachute. We will still be falling faster than the speed of sound at this point, which presents special challenges when opening a parachute. We have designed the parachute to accomodate this speed, and expect it open successfully. The parachute is 11 meters across (about 35 feet). While hanging from the parachute our flight path will be come much more vertical. We will jettison the heat-shield, and open our landing legs. Eventually, we will turn on a radar that will sense the ground below us.

When we are about 1000 meters above the surface (3000 feet) we will let loose of the backshell, and parachute, and complete the descent on thrusters. These will bring us down slow enough that the spring-loaded landing legs will be able to withstand the touchdown force.

... and the entire operations center on Earth will sigh in relief.

***THE PHOENIX LANDER HAS TOUCHED DOWN***
"PHOENIX HAS LANDED, PHOENIX HAS LANDED, WELCOME TO THE NORTH POLE OF MARS"

[7:51 pm]
NGC Viewer: I've always been fascinated by mars as well - but one thing I never understood. How can scientists spend their lives knowing they probably won't learn all that much? I'm one of those - see it to believe it guys.

I'm certainly glad that someone is doing the research, I just wouldn't have the patience.

Robert: While it is true that we are sending people to the Mars any time soon, we are learning an emmence amount. The two chemistry experiments we are carrying on Phoenix have much of the same capabilities that we would apply to unknown samples in an Earth-bound laboratory.

One of the challenges in a mission like this is building experiments that can do what people do, but without the people operating them from close proximity. It is not easy, but it is a lot of fun.
[7:51 pm]
Greg: SOUNDS LIKE ITS GOING GREAT!!! Signal seems to be getting stronger and that the landing is on course. What is the mood like right now in the space operations center?

Robert: Electric! Lots of nerves in the room are a bit frayed. But you know what?

One-way light time is a little more than 15 minutes. That means that EDL has actually already completed; one way or another. We are just patiently waiting to hear about it!

[7:49 pm]
Greg: Well the lander just seperated itself from the rocket, and has begun entering Mars' atmosphere. Check out the video below to get an idea of what is going on.

[7:33 pm]
Matt: We just heard news that NASA was considering a last minute course correction? Can you explain why it wasn't needed?

Robert: The last course correction was considered, and then canceled. We had a series of six "Trajectory Correction Maneuvers". The last of these would have been performed 21 hours before EDL. That TCM was canceled at the last minute because the Navigation team determined that our aim-point was close enough that we didn't need it.

Miles: As far as I know, we have completed all course corrections, but my job does not involve tracking the trajectory. Mars here we come!

15 MINUTES UNTIL LANDING

[7:33 pm]
Greg: So we will be digging through rock and ice right on the surface of Mars, what is your biggest concern with the landing tonight? And what do you see as the biggest obstacle facing tonight's landing roughly twenty minutes out?

Miles: If all goes well, we will get our first images from Mars in a couple of hours. We will looking out on a red sky and the northern plains of a foreign world. Believe me, we will be seeing Mars as if we were there. Our experiments are state of the art, and will inform us about the habitability of the Martian soil. And, one day, these measurements will be what we look back on as the precursor to human exploration. This is the right next step to understanding and exploring Mars.

Robert: Our biggest unknown is the surface we are landing on. We are landing in an area about 20 miles by 60 miles. But exactly where in that area, we don't know. We picked an area that is as clear of big rocks as we could find.
But there are a few. If the lander comes down on a rock such that one leg is up, and the other two are down, we could be tipped enough to make operations difficult if not impossible. We are designed to handle a 16-degree tilt. More than that would ruin our day.

Biggest danger in the first 50 minutes after landing is again the surface.
The first thing we do after touchdown is open our solar arrays. These open like big Japanese fans on either side of the lander. If we land flat on the surface, and there is a big rock right next to us, we may not be able to open the solar array on one side or the other. Here again, our site selection mitigates this somewhat. There are few such boulders in the area where we are landing.

Miles: The biggest obstacle is the unknown. A thousand person-years have gone into Phoenix, and we have made an exhaustive effort to reduce the risk of the landing. Still, there is a possibility that something was missed. Landing on Mars, 270 million km away, is no easy task.

[7:28 pm]
Greg: This almost like a locker room full of excitement before the big game I bet. For many this has to be like a Super Bowl or the World Series. How much of an adrenaline rush is this for you and your colleagues as you potentially could be writing the next chapter in space exploration?

Robert: Each team member is approaching this event from their own mental position.

Yes, some are bouncing off the walls. Having been through this process a couple of times before, I am a little more subdued. We have done all that can be done at this point. The rest of the trip is waiting, and watching.

With only a little more than a half hour before the Phoenix Lander enters the atmosphere, what started as quiet murmur, has started to escalate as the media is setting up cameras and equipment preparing for what's to come. The live commentary broadcast shown on the NASA website flips between interviews with key players in the project, to shots of those waiting anxiously in mission control.

So far, everything looks good. Everyone is waiting in suspense....

45 MINUTES UNTIL LANDING

[7:08 pm]
Greg: How do you feel that the day of the landing has finally come?

Robert: I feel fine. Although, I know a number of my colleagues here who did not sleep well (if at all) last night. I have a high degree of confidence that EDL will be successful. This project has invested enormous effort in making sure we get to the surface safely.

Greg: How are you and your colleagues feeling as we are inching closer?

Robert: The last couple hours here at the operations center have seen a growing excitement. It is palpable. Things were very quiet when I arrived around noon today, now there are audible conversations from many different corners, and offices. You can feel that the moment is approaching.
[6:59 pm]
Greg: Joining us from NASA tonight is Robert Denise. Robert Denise has been helping fly missions to Mars for JPL since 1992, some more successfully than others. His background is in Flight Software Development, and Mission Operations. He lives in Southern California with his wife, and two teenaged children.

Robert why are we so interested in going back to Mars again and again? What is our fascination with Mars and why is it scientifically relevant?

Robert: The question that we keep asking about Mars is this: Where is the water? When we look at Mars from orbiter images, and even from Earth based images, we see evidence of water; huge canyon systems that look like they have been carved by water. The MER rovers have looked far closer at the rocks on the surface, and have found a lot of material that appears to have been formed in the presence of water. But we have not found water on Mars in anywhere near the quantities necessary to make these processes happen.

... and yes, it is facinating.

[6:41 pm]
Greg: Seems like there is some good signs ahead of tonights landing already. We recieved this message from National Geographic Channel Associate Producer Elspeth Johnson earlier today after the noon breifing concluded and gives a great background at what we can expect:

The noon briefing just concluded. There is a lot of optimism going around the room as the final hours of approach are coming to a close. Martian activity has started as the gravitational pull is speeding up the Phoenix Lander. At 8:30am PDT time this morning, the Lander was going 6300mph, by 12:30pm(PDT) was going approx 8500mph. They predict that by 4:30pm PDT, as it enters the atmosphere it will be traveling at a speed of 12,700 mph. This leaves 7 minutes for it to slow to 0mph for landing also referred to as the 7 minutes of terror. The Lander is about 30,000 miles away from Mars and the hope is that horizon pictures will be visible before it enters the atmosphere. Once the Lander separates from the engine, it will be be running on battery power only. With 90% of speed and energy slowed, it will be going about 1100mph. Once the parachute is deployed, releasing 10,000lbs of pressure, it will slow the Lander down to around 120mph. And once the rocket thrusters activate, it will take the Lander down to 5mph and 100ft to go. They predict 15min. for the dust to settle. After the 15 minutes, the radio transmission will be the first signal that it landed safely. They have included several safety mechanisms to the Lander so that it can function even if something is a little off....ex. it can function at a 16% tilt. Once the transmissions come through, the Odyessy satellite will start bringing in pictures; it is scheduled to orbit around at 6:45PDT and has a fifteen minute delay. Pictures are projected to be around 7:00pm PDT or 10:00pmEST.

[6:20 pm]
Greg: GOOD EVENING NAT GEO CHANNEL AND NASA FANS!

We are a still a little over an hour away from the first signal from NASA's Phoenix Lander. But we here at the channel didn't want to wait to get things going.

We have one associate producer embedded at the operation center, we have our operations team monitoring the feed that you see directly to your left and they are also been a big part in making sure everything runs smoothly on our side tonight - shout out to Fletch and his great team! - , and then you have the group you will be hearing from tonight, NASA Engineers Robert Denise and Miles Smith, Nat Geo's Digital guru Matt Zymet and myself, Greg Chapman.

Please feel free to send us your questions or comments about tonight's landing right here on the NGC Blog.