Emily Lakdawalla continues her excellent blog coverage in this article, which does a great job of explaining some of the reasons why this image was especially difficult to take. Along the way, she includes a tutorial on TDI (Time-Delay-Integration), written by one of the engineers that helped build the instrument. TDI is the method HiRISE uses to gather lots of light into its CCDs, and it’s one of the reasons we get such high signal-to-noise in our images. It’s a complicated concept, but it’s an important one for understanding HiRISE’s incredible imaging abilities, as well as its limitations.

From her blog post:

This is a fascinating story showing how necessary it sometimes is to have a deep understanding of an instrument in order to understand the data that comes from it. …It can be dangerous to read too much into space images until you have studied how the cameras really work.

It’s a great post – she deserves a cookie!

MRO did a special imaging sequence to slew over to where the Phoenix spacecraft was plummeting down through the atmosphere, and it WORKED! I can’t believe what an engineering feat this was – the MRO spacecraft team’s pointing was right on, and Phoenix was exactly where they thought it would be.

When I left last night, we hadn’t gotten down the channel that included the parachute. The rest of the image is pretty low signal (and it’s a HUGE image), so we were searching through it for hours, trying to separate out cosmic ray hits and bright patches of ice. They had only given us a ~20% chance of getting it in our field of view, so I thought we had missed it. I finally went to bed feeling pretty frustrated, but woke up to find that, overnight we received additional channels of the image, and Richard Leis and some others here at HiROC had found THIS!

You can see the parachute itself, AND the lander encased in the heat shield dangling below it – AND you can see the STRINGS attaching them! This is the first time a spacecraft has ever been photographed as it descends through the atmosphere of another planet. Everyone here is incredibly excited about this image.

However, we’re too busy poring over the image we took after this one to spend too much more time on this. Hopefully soon we’ll be able to show you the lander itself, on the surface!

Go, Phoenix!

NASA press release: http://www.nasa.gov/mission_pages/phoenix/news/phoenix-20080526.html

When Peter Smith gave enthusiastic shout outs to the UofA community and to Arizona, the crowd erupted in responsive applause. Congratulations to the Phoenix team and especially to those working on EDL at JPL in Pasadena and Lockheed in Denver.

Detailed schedule of events:
http://www.lpl.arizona.edu/calendar/calendar.php?ID=107

We’ll be thinking of the Phoenix team during this critical step – we’ve got our fingers crossed, wishing you the best!

We’ve been imaging the northern plains for Phoenix since we started our mission (here’s a bunch of reconnaissance images on our website). The first images we got back showed lots of scary boulders (a close-up of one of our Transition images shown to the right), so we sampled other areas and searched for a relatively boulder-free landing spot. The area the Phoenix team finally chose is being called the “Green Valley“, not because of the “green light = safe to go” connotation, but rather because some geological maps made of the area happened to use green as the color for the valley. Perhaps coincidentally, Green Valley is also a town near Tucson, where both Phoenix and HiRISE are based. Whatever the reason, I like that the name has a lovely calm, comforting feel.

Once the Phoenix team picked out their landing site, we worked on a high-resolution mosaic of the entire 3-sigma landing ellipse (”3-sigma” means there is a 99% probability it will land within this area; see this great blog entry on landing ellipses at the Planetary Society). The Phoenix landing ellipse is shown to the left, along with the footprints of a number of HiRISE images. (This was before we were quite done with the mosaic.) These images have helped the Phoenix team characterize the regional geology and assess the safety of the landing site.

In addition to scouting landing sites, we’re also going to be involved with Phoenix during its prime mission on the ground. We’ve been planning and practicing several different ways of cooperating:

• Early Imaging: We are going to attempt to take observations of Phoenix on the ground several times in the first week of the mission. There are three images planned, two on the first day and one on “sol 5″. (The Pheonix mission will be counting time in Mars days, or “sols.”) Since the first two images are so early, there’s a good chance we won’t know quite where it landed yet, so the chances of seeing it are slim. The sol 5 image should be really good, though – we’ll know the exact landing spot by then, plus the image will have ideal lighting conditions and the highest resolution we can get.
• Relay: The Electra instrument on MRO will relay commands from Earth to the Phoenix lander, and it will relay data from Phoenix back to Earth. This affects HiRISE only indirectly – we’ll be planning our science imaging around the times Electra needs to be communicating with Phoenix.
• Cooperative Science: Phoenix and MRO have been planning coordinated science observations using different instruments on both missions. For example, when Phoenix takes a measurement of the amount of ice on the ground, they might want an image from HiRISE at the same time, to see how much frost is visible in the surrounding area.

Landing will be just the beginning of all these exciting activities. Come join us for a public celebration on landing day, May 25th! There are all sorts of events planned: