(If you like that chart, you can find a live-updated version here.)

Philae's status: Warm with plenty of power

The initial report showed Philae with plenty of power (24 watts) and, if not warm by Earth definitions, at least not too cold (-35ºC). A later, briefer burst of telemetry showed the lander even warmer, -5ºC. The initial packets of data from the lander indicated that it had been awake for at least a few days, possibly as long as a few weeks, before successfully making contact. A Rosetta blog entry from Monday tells us that the lander began generating about 13 watts at comet sunrise, reaching a high of more than 24 watts at noon, and that the solar panels are receiving more than 135 minutes of sunlight each comet day. (The comet rotates once in 12.4 hours, so that's still a short day and a long night, but it's enough for Philae to be active.)

This is more than enough power for science, especially for instruments that require less power (like ROMAP, the magnetometer). Early work "would also likely include measurements that did not previously generate science in November," the blog entry states (more on that below). But before they can do science, they need to improve the stability and quality of communications between orbiter and lander. Rosetta's orbit is not currently a good one for long periods of high-quality lander communications. So the next order of business is to shift Rosetta's orbit to one that can support robust communications. They will shrink Rosetta's orbit to a 180-kilometer one, and keep the orbiter aimed downward toward the comet's surface.

The ESA blog notes that the unfortunate events of Philae's landing, which were so frustrating in November, are now beneficial for the lander; shadowing keeps its temperature from rising too high now. "Any operation of Philae’s instruments up to or through perihelion on 13 August – the comet’s closest point to the Sun along its orbit – will allow in-situ study of a comet during its peak activity. Had Philae landed at the planned site, at Agilkia in November 2014, its mission would likely have ended in March because of the higher temperatures of that location as solar illumination increased."

Philae's activities: what's next?

Once Rosetta can communicate more reliably with Philae, the mission will be able to get back to work. They held a press briefing at the Paris Air Show today to explain the current status and future plans for the mission. You can watch the whole briefing below:

Here are some key points from the briefing.

From Elsa Montagnon, deputy flight director for Rosetta: The comet is very active at the moment. There have been numerous "star tracker events" in which the spacecraft's star trackers confuse dust particles for stars, and lose their ability to determine the spacecraft's orientation. The number of star tracker events is continuing to increase as the comet approaches perihelion. Perihelion is on August 13. Based on current activity levels, the mission has determined that the closest safe distance for Rosetta to the comet is 180 kilometers. But if comet activity increases, they will have to retreat. At present, the Rosetta mission is planned to end on December 31. However "we know we have enough resources until September 2016." It was not clear whether she meant financial resources or spacecraft resources -- I would assume she meant the latter, but don't know for sure. By that time, comet activity will have decreased markedly.

From Barbara Cozzoni, a Lander Control Centre engineer: Analysis is ongoing to understand and calculate exactly when the lander first switched on; it was "probably days before" June 13. Both of the computers (DPUs, Data Processing Units) are working. The computer's software is able to detect the day/night cycle on the comet. The lander internal compartment is warm, already at -36C at sunrise. Its minimum operating temperature is -45C. Four solar panels (1, 2, 3, and 6) are collecting energy. Moreover, they are performing in line with predictions, meaning that no comet dust has settled on them to obscure them. "So it looks like Philae is ready for operation now." But to be really sure they need more data, and for that they need Rosetta to be in a better orbit.

They are now getting ready to do science. "In the last seven months we were not only praying for the lander to come back; we were also planning." They plan to begin long-term science in the next few days. Science plans will take the form of science "slots," each lasting a single comet day. Some slots will be used for charging the batteries, because some science operations require battery power. Science observations will be performed autonomously. They don't need daily Rosetta communications to make this work, but they do need to know how many slots will pass in between opportunities to communicate with the orbiter, so they need predicted contact times from Rosetta.

From Philippe Goudon, Philae project manager at CNES: in November, Philae accomplished about 80% of the goals of its first science sequence. The two things it did not do were to measure the surface with APXS and to collect a sample with SD2 and deliver it to COSAC and Ptolemy. They had intended to land in a spot in the northern hemisphere, which would have given them 9 hours of sunlight out of the 12.4 hour day. It would also have killed the lander after March. Instead, they landed in the southern hemisphere during winter. The main reason that the power situation has improved is that the comet is now much closer to the sun, but the change in seasons has also helped. The best time for lander power will be in August because the comet will be close to the sun and because there will be the longest days.