Chandrayaan-1 is the Indian Space Research Organisation’s (ISRO) mission to the moon, with the main scientific objectives of photo-selenological and chemical mapping of the lunar surface. It was successfully launched from Satish Dhawan Space Centre, Sriharikota on October 22nd 2008 at 06:22 local time. The total mission is expected to last for two years.
X-ray Solar Monitor (XSM) is a part of the payload selected for Chandrayaan-1. It is an improved version of the instrument already flown on ESA’s SMART-1 mission. XSM will measure the X-ray spectrum of the sun and act as a calibration system for the C1XS instrument provided by the Rutherford Appleton Laboratory (RAL, UK). The combined C1XS-XSM data will give an absolute abundance measurement of the elements on the surface of the moon. In addition to being a part of the C1XS measuring system, XSM will provide significant independent information about the solar corona.
The XSM instrument consists of two main parts, the sensor unit and the main electronics board. The sensor unit contains a Peltier cooled high purity silicon PIN radiation detector, the detector’s front-end electronics and an electro-magnetically controlled shutter for shielding the detector from radiation when it is not in use. The shutter also has a calibration source mounted on it, to allow in-flight calibration of the detector. The XSM main electronics board, situated in the C1XS housing, contains all the necessary processing and controlling functions of the instrument.
The design, fabrication and testing of XSM was done by Oxford Instruments Analytical Oy, in close collaboration with the Observatory at the University of Helsinki. The calibration was performed at the X-ray Laboratory of the University of Helsinki.