Fw: Keeping MESSENGER Cool

[LARRY KLAES]

----- Original Message ----- From: MESSENGER News Sent: Tuesday, December 30, 2003 3:40 PM To: MESSENGER News Subject: Keeping MESSENGER Cool   MESSENGER Mission News December 30, 2003 messenger.jhuapl.edu     Keeping MESSENGER Cool   While orbiting Mercury, MESSENGER will "feel" significantly hotter than spacecraft that orbit Earth. This is because Mercury's orbit swings the planet to within about 46 million kilometers (29 million miles) of the Sun, or about one-third of the distance between the Sun and Earth. The Sun also appears 11 times brighter at Mercury than we see from our own planet.   Without extra protection in such an extreme environment the spacecraft and its instruments would overheat and cease to function - but MESSENGER engineers answered this challenge by designing a heat-resistant and highly reflective sunshade. The team installed the 254-by-180 centimeter (8-by-6 foot) shade on Dec. 12, shortly before moving the spacecraft to NASA Goddard Space Flight Center for prelaunch tests.   The thin sunshade is a high-tech parasol constructed from Nextel ceramic cloth, with several inner layers of Kapton plastic insulation. While MESSENGER's Sun-facing side could heat to above 310� Celsius  (590� Fahrenheit) during the orbit, preliminary tests and thermal analyses show the sunshade will keep the spacecraft operating near room temperature, around 20� C (or 68� F)   In this week's annotated Webcam image, a MESSENGER team member covers the spacecraft's forward-side phased array antenna with its custom-fitted shade. Click here to see an image, taken several minutes later, with the full sunshade installed.     Build your own MESSENGER spacecraft! Click here to download the model and directions. (You'll need Adobe Reader to open the file.)      MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a scientific investigation of the planet Mercury, and the first NASA mission designed to orbit the planet closest to the Sun. Dr. Sean C. Solomon, of the Carnegie Institution of Washington, leads the mission as principal investigator. The Johns Hopkins University Applied Physics Laboratory in Laurel, Md., is building and will operate the MESSENGER spacecraft and manages the Discovery-class mission for NASA.   For more information on the mission, visit http://messenger.jhuapl.edu.