Mars Express Orbiter Buzzes Martian Moon Phobos

astroengine writes "On Sunday, at 5:17 p.m. GMT (12:17 p.m. EST), Europe's Mars Express orbiter successfully completed a daring low-pass of Mars' largest moon Phobos. In an effort to precisely measure the gravitational field of the moon, the 10 year-old mission was sent on a trajectory that took it only 45 kilometers (28 miles) from the dusty surface, the closest any spacecraft has ever come to the natural satellite."

Comments

On the surface

[mbone]

Here is a simulated view of the Mars Express pass from the surface of Phobos. https://www.youtube.com/watch?v=Z-YlKEKt-_k

However, the simulation missed something - Mars Express has a 40 meter dipole antenna - at 45 km, that's 3 arc min, so you could see Sun glint on the dipoles with your naked eye (i.e., you could resolve it as a structure, not just a dot of light). With a pair of binoculars, you could even see the spacecraft's solar panels.

No pictures this time

[mbone]

This was a radiometric (Doppler tracking) pass, with the main antenna pointed at the Earth. Pictures would have required re-orienting the spacecraft, and ideally rotating it to remove any motion blur on the close approach. You cannot do that and keep lock on the Earth, and they wanted to nail down the mass of Phobos. Initial reports from the DSN are the the Phobos gravity Doppler shift was visible in the "raw" residuals, so it's likely they will meet this goal.

Small...very small moon.

[dubdays]

The dimensions of this moon is only 13.4 × 11.2 × 9.2 km. Pretty tiny, it seems to me, for a planet the size of Mars.

Re:Wow. What a moon.

[MichaelSmith]

What a crappy black rock.

Okay, I was wrong...the photo was black and white. It would have been nice if they shot it with a color camera (unless, of course, that's coming later).

Color photography from spacecraft is a sub-disipline of spectroscopy. They take monochrome images with different filters, then produce color pictures from the composites.