PASADENA, Calif. — The larger of the two moons of Mars, Phobos, passes directly in front of the other, Deimos, in a new series of sky-watching images from NASA’s Mars rover Curiosity.

A video clip assembled from the images is at http://youtu.be/DaVSCmuOJwI .

Large craters on Phobos are clearly visible in these images from the surface of Mars. No previous images from missions on the surface caught one moon eclipsing the other.

The telephoto-lens camera of Curiosity’s two-camera Mast Camera (Mastcam) instrument recorded the images on Aug. 1.  Some of the full-resolution frames were not downlinked until more than a week later, in the data-transmission queue behind higher-priority images being used for planning the rover’s drives.

These observations of Phobos and Deimos help researchers make knowledge of the moons’ orbits even more precise.

“The ultimate goal is to improve orbit knowledge enough that we can improve the measurement of the tides Phobos raises on the Martian solid surface, giving knowledge of the Martian interior,” said Mark Lemmon of Texas A&M University, College Station.  He is a co-investigator for use of Curiosity’s Mastcam.  “We may also get data good enough to detect density variations within Phobos and to determine if Deimos’ orbit is systematically changing.”

The orbit of Phobos is very slowly getting closer to Mars. The orbit of Deimos may be slowly getting farther from the planet.

Lemmon and colleagues determined that the two moons would be visible crossing paths at a time shortly after Curiosity would be awake for transmitting data to NASA’s Mars Reconnaissance Orbiter for relay to Earth. That made the moon observations feasible with minimal impact on the rover’s energy budget.

Although Phobos has a diameter less than one percent the diameter of Earth’s moon, Phobos also orbits much closer to Mars than our moon’s distance from Earth. As seen from the surface of Mars, Phobos looks about half as wide as what Earth’s moon looks like to viewers on Earth.

via NASA Rover Gets Movie as a Mars Moon Passes Another | NASA.

Following months of analysis and testing, the Kepler Space Telescope team is ending its attempts to restore the spacecraft to full working order, and now is considering what new science research it can carry out in its current condition.

Two of Kepler’s four gyroscope-like reaction wheels, which are used to precisely point the spacecraft, have failed. The first was lost in July 2012, and the second in May. Engineers’ efforts to restore at least one of the wheels have been unsuccessful.

Kepler completed its prime mission in November 2012 and began its four-year extended mission at that time. However, the spacecraft needs three functioning wheels to continue its search for Earth-sized exoplanets, which are planets outside our solar system, orbiting stars like our sun in what’s known as the habitable zone — the range of distances from a star where the surface temperature of a planet might be suitable for liquid water. As scientists analyze previously collected data, the Kepler team also is looking into whether the space telescope can conduct a different type of science program, potentially including an exoplanet search, using the remaining two good reaction wheels and thrusters.

“Kepler has made extraordinary discoveries in finding exoplanets including several super-Earths in the habitable zone,” said John Grunsfeld, associate administrator for NASA’s Science Mission Directorate in Washington. “Knowing that Kepler has successfully collected all the data from its prime mission, I am confident that more amazing discoveries are on the horizon.”

On Aug. 8, engineers conducted a system-level performance test to evaluate Kepler’s current capabilities. They determined wheel 2, which failed last year, can no longer provide the precision pointing necessary for science data collection. The spacecraft was returned to its point rest state, which is a stable configuration where Kepler uses thrusters to control its pointing with minimal fuel use.

via NASA Ends Attempts to Fully Recover Kepler Spacecraft, Potential New Missions Considered | NASA.