As of this posting, we are just 2 days, 12 hours, and thirty minutes away from the Curiosity rover making touchdown on Mars. We're excited. NASA's excited. Even Angry Birds is excited.
And really, why shouldn't they be? Curiosity is the most scientifically impressive rover ever built. Its arrival on Mars is hands down the craziest planetary landing ever attempted in the history of space exploration. With all the milestones NASA is planning on crushing with the landing of Curiosity, isn't anyone the least bit interested in capturing some third-person footage of the rover's arrival — a nice, big photograph of the spacecraft soaring through the Martian sky, on its way to the northwest basin of Gale crater? Why yes, someone is. And they'll be using an entirely different spacecraft, already in orbit around Mars, to do it.
The spacecraft in question is the Mars Reconnaissance Orbiter, which has been circling the Red Planet for a little over six years now. The MRO is equipped with HiRISE, the most powerful camera we've ever sent to another planet. Back in January, HiRISE Principle Investigator Alfred McEwen told us that the HiRISE imaging team would attempt to image the rover as it's descending to the planet's surface on the sky crane, pictured here. But according to Christian Schaller, who develops the planning tools that HiRISE targeting specialists use to plan their images, the goal is to now photograph Curiosity during the parachute stage of its arrival — similar to the image up top of NASA's Phoenix lander, captured in May, 2008. According to Universe Today:
The HiRISE camera crew on the Mars Reconnaissance Orbiter will attempt an audacious repeat performance of the image above, where the team was able to capture an amazing shot of the Phoenix lander descending on a parachute to land on Mars' north polar region. Only this time it will try to focus on the Mars Science Laboratory's Curiosity rover descending to touch down in Gale Crater. It will be all or nothing for the HiRISE team, as they get only one shot at taking what would likely be one of the most memorable images of the entire mission for MRO.
"We're only making one attempt on MSL here," Christian Schaller of the HiRISE team told Universe Today. "The EDL (Entry, Descent and Landing) image is set up so that as MSL is descending, MRO will be slewing the HiRISE field of view across the expected descent path. The plan is to capture MSL during the parachute phase of descent."
As you've probably guessed, photographing a spacecraft that's hurtling toward the surface of a planet at several hundred miles an hour from another, different spacecraft that is orbiting that same planet, all from a distance of 350-million miles, will be... challenging.
"We were somewhat lucky [with the Phoenix lander] in that there was a fairly large error ellipse (uncertainty about about where [Phoenix] would be at the time we were imaging);" says McEwen, "but our geometry was such that we managed to cover most of it, and had somewhere in the neighborhood of 80% chance of success of imaging [Phoenix] as opposed to missing it."
"We may not be as lucky [with Curiosity]."
Having said that, it's worth pointing out that Curiosity's predicted landing ellipse is considerably smaller than what we've seen on previous missions to Mars (the image featured here shows the size of Curiosity's landing ellipse relative to that of its predecessor, the Spirit rover), a fact that McEwen says could help make imaging Curiosity's descent a more manageable task. It'll still be a challenge, but Schaller, for one, sounds confident:
"We've been gradually updating the exact timing of [the rover's entry, descent and landing sequence] over the past couple of weeks as the MSL navigation team, the MRO navigation team and the MRO flight engineering team refines that descent path and MRO slew," Schaller told Universe Today via email, "and we think we've pretty much got it nailed down at this point."
"I think it's a real testament to NASA and its partners that we can even think about doing this."