“Seven Minutes of Terror” — that’s what NASA’s Jet Propulsion Laboratory, where I worked for 10 years before leaving to work on True full time, went through yesterday.
12,750 mph to Zero in 7 Minutes
The Phoenix lander arrived at the top of Mars’ atmosphere after a 9-month voyage, and it was moving at about 12,750 miles per hour. It had to “hit the brakes” (mainly with atmospheric drag and a super-high-strength parachute, but also at the end with rockets), and get down to just 5 mph for its soft landing on the surface just 7 minutes later.
It wasn’t an easy task: before yesterday, Mars landers had a 55 percent failure rate, which is why the mission control people at JPL call it the “seven minutes of terror” — when you’re going that fast, even something terribly minor going wrong can make the difference between success and a new surface crater.
I was watching when they landed Sunday afternoon, and smiled at the cheers. A couple of hours later, the first images arrived: a look at the lander’s solar panels to ensure they deployed properly (since if not, they would have limited time to send up commands to fix things before the batteries give out).
A quick look at the landing pads to ensure they’re on firm soil. And then a panorama to see their immediate surroundings. All was well.
It was the first soft landing on Mars in 32 years. (Two of the three Mars rovers are still working there, long after their expected lifespans; they hard landed — a controlled crash landing on the surface, protected by airbags. They couldn’t do that with Phoenix because it’s too heavy and fragile.)
Sending a Photographer
One cool thing that I didn’t know they were going to do: they timed things so that during the landing near Mars’ north pole, the Mars Reconnaissance Orbiter would be overhead. It actually got a photo of Phoenix under its parachute! MRO has been orbiting Mars since March 2006.
MRO was at an altitude of 472 miles (760 km), or about double the altitude of the space station currently orbiting Earth. At the time of the snap, Phoenix was about 7.8 miles (12.6 km) above Mars. In the resulting photo (below), Mars is completely dark because they were trying to capture the much-brighter spacecraft. You can (barely) see the parachute’s cords. Astounding.
Peter Smith of the University of Arizona in Tucson is the mission’s Principal Investigator. His mission with Phoenix is to study the history of the water now frozen into the site’s permafrost, to check for carbon-containing chemicals that are essential ingredients for life, and to monitor polar-region weather on Mars from a surface perspective for the first time. JPL is in charge of project management.
In addition to NASA support, Phoenix is supported by the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus, Denmark; Germany’s Max Planck Institute; and the Finnish Meteorological Institute. For more on the mission see its NASA home page or its University of Arizona home.
I didn’t work in JPL’s Mars Program myself, but I was, and am still, friends with the former Mars Exploration Program Manager, Donna Shirley, who retired in 1998 after the tremendous success of the Mars Pathfinder rover and Mars Global Surveyor missions. Donna was the highest-ranking JPLer to come to my going-away party, and is one of those people who enjoys intelligent, thought-provoking humor — otherwise known as a This is True reader.
Here’s a nice video by JPL about the Phoenix landing:
Update from Donna
When she read the above, Donna Shirley commented:
Actually, Phoenix is no heavier than the MER rovers. It landed with thrusters because the 2001 lander, which Phoenix originally was, was based on the 1998 lander, which failed for a number of reasons, primarily too many requirements and not enough money. After this 1998 failure NASA decided to mothball the 2001 lander at Lockheed Martin and use all the money to fly the orbiter, now called Odyssey, which is still operating successfully. In fact Odyssey was the main comm relay for the Phoenix landing. Peter Smith resuscitated the 2001 lander to make an affordable 2008 Phoenix mission. Phoenix used thrusters for landing because the 1998 lander was designed before the success of Pathfinder at a time when most people, especially the contractor Lockheed Martin, thought airbags were crazy. When Pathfinder worked successfully the MER landers were designed with airbags. However, the Mars Science Laboratory, scheduled for 2009 or 2011 depending on whether they can get the many problems fixed, will use a thruster landing because it is indeed too heavy for airbags. The MER landers were barely light enough for airbags.
The MSL lander will, however, not land with thrusters either. The plan is to lower the rover/lander with thrusters and rappel the rover down on a cable to the surface so the “lander” never touches the surface. It cuts off the rover and rockets away to crash on the surface.
For more info on the MSL, see the MSL Project Site.
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