24 Feb. 2011

 

A family portrait of the solar system

 

Using the Wide Angle Camera (WAC) and the Narrow Angle Camera (NAC) of the Mercury Dual Imaging System (MDIS) on-board NASA's MESSENGER probe (MErcury Surface, Space, ENvironment, GEochemistry, and Ranging), the first solar system mosaic has been obtained, as seen from near Mercury. MESSENGER will enter into orbit around this planet on 18th March.
This image, very difficult to make (due to the strong constraints on pointing caused by the proximity of the Sun and the need to have all the planets visible at once) was realised by a team led by Sean Solomon (MESSENGER Principal Investigator). The mosaic is composed of 34 images taken last November with the WAC, and was augmented by close-up images of each planet taken with the NAC.
Each image is the average of three 10 second exposures, so as to reduce image noise. 10 seconds is actually the longest exposure time possible with MDIS, clearly not designed with this kind of imaging in mind. As a consequence, the more distant planets, Uranus and Neptune, are not detected, although their locations are indicated in the image.
The inclination of MESSENGER'S orbit with respect to the ecliptic at the time the images were taken causes the mosaic to have a sinusoidal shape. Some interesting features visible include the Moon, the Galilean satellites of Jupiter and part of the Milky Way. The original mosaic was actually less elongated, but the authors preferred to apply a stretch for greater clarity, even though the operation results in slightly distorted planetary disks.
This view taken from the inner solar system is a complement to that taken from the outside by Voyager 1 in 1990, and visible at: www.jpl.nasa.gov/news/news.cfm?release=2010-048. Also on this occasion, it wasn't possible to image Mercury, not because it was too close (as was the case for MESSENGER) but rather because it was immersed in the Sun's glare. The same problem, that is, the glare of the central star, is actually what hinders the detection of extra-solar planets.

 

by Michele Ferrara & Marcel Clemens

credit: NASA/Johns Hopkins Univ. Applied Physics Lab./Carnegie Inst. of Washington