UPDATE 21:30 UT: RIA Novosti reports that ESA representative Rene Pishel stated that Perth successfully received telemetry from Phobos-Grunt and has forwarded the data on to Lavochkin for analysis. He also stated that the communications session lasted only six minutes, so cautioned that the amount of data received may be very little.

Still, the facts that the spacecraft can (1) hear commands from Earth (2) respond to them correctly and (3) broadcast a signal to Earth are all very, very good news.

On Tuesday, November 22 at 20:25 UTC, a European Space Agency ground station in Perth, Australia, successfully made brief radio contact with Phobos-Grunt. It is the first time that the spacecraft has talked to the ground since just after its separation from the upper stage of the Zenit rocket on November 8. In order to make contact, the ground station had to transmit a command to the spacecraft to switch on its transmitter. The spacecraft heard and responded to the command by switching it on, broadcasting a carrier signal but no telemetry. ESA detected the transmitted signal.

ESA's Perth radio tracking station ESA's Perth station is located 20 kilometres north of Perth (Australia) on the campus of the Perth International Telecommunications Centre (PITC), which is owned by Telstra, and operated by Xantic. This antenna is 15 meters in diameter and has a 1.3-meter "search antenna" mounted to its side. Credit: ESA

The next steps involve using the Perth station to attempt to receive telemetry. RIA Novosti quotes an ESA official, Rene Pishel, as saying that five attempts are planned over Wednesday night and Thursday morning: 20:25, 21:57, 23:32, 04:16, and 05:49 UTC.

In order to make contact, the Perth station had to overcome several significant challenges requiring modifications to their ground station. Although Phobos-Grunt has been tracked since launch by optical telescopes, its orbit was not known precisely enough for controllers to aim the radio antenna's narrow beam. Also, Phobos-Grunt's receiver is designed to receive extremely faint signals, and the ground stations broadcast with too much power. So they added a feedhorn antenna to one side of the main dish that could transmit a signal at much lower power and over a much wider cone of the sky. It was using this new feedhorn to transmit the command to Phobos-Grunt that they successfully commanded the spacecraft to switch on the transmitter, which they picked up with their larger dish. The BBC reports that as a byproduct of their reception of the signal, they were able to reduce the uncertainty of their knowledge of the spacecraft's orbit.

The Phobos-Grunt feedhorn View of the Perth 15-meter antenna showing the feedhorn antenna mounted near the small, 1.3-meter search antenna, both mounted at the side of the main dish. The mini-antenna was used to send telecommands to Russia's Phobos-Grunt mission in Earth orbit on November 22, 2011. Credit: ESA

Other challenges result from the low and fast orbit occupied by the spacecraft. To communicate with a ship in low-Earth orbit, the ground station must be able to turn quickly (a capability the antenna already had), as well as to receive a signal whose frequency varied substantially over the very short period in which contact was possible because of the Doppler shifts caused by the spacecraft's fast motion.

There is no question that hearing from the spacecraft is good news, providing a hope that the mission may be salvaged. But it's not time to celebrate just yet. Russia is far from having a commandable spacecraft prepared to go on to another planet.

Why might ESA have been able to establish contact when Russia could not? The answer has to do with the geometry of the spacecraft's orbit. Phobos-Grunt circles Earth 16 times a day, and it spends half of each of those orbits in shadow -- a condition that deep-space spacecraft are not usually designed to experience except in unusual circumstances around launches and arrivals. While Phobos-Grunt is over Baikonur, it has been in shadow. While it is over Perth, it is in sunlight. So -- keeping in mind that this is statistics of small numbers we're talking about -- the success from Perth may indicate that for some reason Phobos-Grunt can only communicate with Earth while it is in sunlight and solar panels are receiving power.

An unnamed source told RIA Novosti that the spacecraft may power off 16 times a day when it enters Earth's shadow. In a spacecraft configured for interplanetary flight, the source speculated (I think it's speculation -- I don't know how confident the unnamed source is in this information), the detection of no power coming from the panels would be an anomaly that would require the spacecraft to go into some emergency mode.

RIA Novosti has set up an index page for its coverage of the successful communication session with Phobos-Grunt and the following events. There are various discussions about what Russia might do if it reestablishes control of Phobos-Grunt -- take it to Mars but not back, take it to the Moon, take it to a near-Earth asteroid -- but all of these are premature until control is established and the state of health of the spacecraft is understood, so I don't plan to report on them.

http://planetary.org/blog/article/00003272/

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As I was beginning my research for my two magazine articles on the Curiosity rover's upcoming mission to Mars, I needed to figure out for myself how exactly this gigantic, ungainly machine fit in to the context of past Martian missions. Clearly, Curiosity was bigger than Spirit or Opportunity and much bigger than Sojourner. That's no great insight; JPL published a "rover family portrait" that nicely summarizes the way JPL's rovers have grown and changed from the teeny Sojourner to the graceful, human-scale Mars Exploration Rover, to the nuke-powered Curiosity.

Rover family portrait Full-scale models of three generations of Mars rovers: Sojourner (center), which landed with Mars Pathfinder on July 4, 1997; the Mars Exploration Rovers Spirit and Opportunity (left), which landed on Mars on January 4 and 25, 2004; and Mars Science Laboratory Curiosity, set to launch for Mars in November or December of 2011. Credit: NASA / JPL

But how much bigger, and why? One of the first things I did was to put together a table of the three rovers, comparing their masses, their instrument payloads, and so on. It was clear from the table that Curiosity is as big as she is because she's hauling around an instrument package 100 times the size of Sojourner's, and a still-impressive 13 times the size of Opportunity's. This is so outrageously oversized compared to past missions that I needed to find some other context. A bit of web searching made me realize that there has been something with such a huge and (for its time) complex payload sent to Mars before: the Viking landers. Here's my comparison table, among the three rovers and the Vikings. I wondered: is Curiosity really just Viking on wheels?

When I interviewed Matt Golombek (who led the selection of Spirit, Opportunity, and Curiosity's landing sites and who was the principal investigator on the Pathfinder mission, which carried Sojourner to Mars) I asked him whether one can get away with calling Curiosity "Viking on wheels?"

Matt said it wasn't a bad characterization but that there were a few really dramatic differences. Curiosity, like Viking, carries a tremendously capable analytical laboratory suite. These are instruments where you grab a sample from out in the Martian environment and bring it inside the spacecraft into a controlled environment. In that controlled environment, you can run a number of experiments on these selected samples. As with Viking, most of Curiosity's payload resides in these sophisticated analytical laboratory instruments. So a significant amount of time on the mission will be devoted not to driving, but rather to identifying, collecting, preparing, delivering, and analyzing samples. Remember the arduous challenges of obtaining and delivering samples on Phoenix? Curiosity's sample collection and delivery will hopefully go better than Phoenix' did, but it probably won't go much faster.

The main difference between Curiosity and Viking instrument suites reside in the questions they were seeking to answer. The Viking landers were sent to Mars with the overarching question: is there life on Mars? Unfortunately, the answers were equivocal. Matt assured me that the Mars program learned a lesson well from Viking. The question that Curiosity is seeking to answer is: was or is Mars a place that had the conditions necessary to support life? The reason that this is a better question is that we will learn a great deal about Mars even if the answer to this question winds up being equivocal. The Vikings went to Mars to search for life and didn't find it. What does that mean? Is there no life on Mars? Was there once, but there isn't now? Is there or was there life, but we just looked in the wrong place or in the wrong way?

"In a sense," Matt told me, "We swung for the fences, and we struck out. You spent most of your money on a negative result. Okay, we learned a little bit about the chemistry and mineralogy of the soil (more chemistry than mineralogy), but that isn't what you spent all that money to do."

Curiosity's instruments aren't out to detect life. They are out to describe Mars' environment, past and present, in greater detail than ever before, much more so than was possible with Spirit and Opportunity's instrument suites. "The major difference for us geologists," Matt said, "is that we'll get dramatically more definitive chemistry and mineralogy. On MER we kind of infer mineralogy from Mini-TES and Moessbauer. But that's becoming difficult now that the Mini-TES isn't working anymore, and the Moesbbauer takes so long to get spectra that we don't use it very much. When you put something in an XRD and XRF" (these are the complex analytical tools in Curiosity, the instruments called CheMin and SAM), "you get incredibly detailed information about the mineral structure, as well as the geochemistry about what's in those minerals, far beyond what we've gotten from any mission sent to Mars. Far, far beyond.

"MSL's going to look at the same materials we've seen with all the other Mars missions with some fresh instruments. It won't matter whether we find phyllosilicates or not, we're going to learn a huge amount about the materials. if you know what the minerals are and the layers are, you know what the environment was. That's the most compelling part -- we don't know whether [prebiotic chemistry] ever began on Mars; it's kind of a needle in a haystack search, and you don't want to only do that. You want to get all that basic information, what the environment was, was it conducive to life, and were the building blocks for organic materials available. We'll answer those questions regardless of whether there's actually organics. If we find them, it's a great bonus. But if we don't, that's okay too, we've still made a major step forward."

I'll be explaining Curiosity's instrument suite in more detail tomorrow. But today, I'll leave you with this picture. Curiosity is clearly descended from JPL's past six-wheeled, insect-legged, mast-camera'd, robotic-armed rovers. But its scientific roots go all the way back to those first footpads that ever touched down on the Red planet. Curiosity truly represents the culmination of a campaign that NASA has (almost) relentlessly pursued for the last 36 years.