Chandra X-Ray Observatory

Launched aboard space shuttle columbia from Kennedy Space Center on 23rd July 1999, The Observatory is named after a Nobel Prize winner, Indian-American astrophysicist Subrahmanyan Chandrasekhar. The telescope is specifically designed to observe the X-Ray sources in the universes such as Galaxy clusters, exploded Stars, and matter around Black Hole. 

Chandra Specifications

Overall Size	13.8m x 19.5m (45.3ft x 64 ft)
Overall Weight	4800 kg (10582 lbs)
Telescope Weight	956.4 kg (2108 lbs)
Focal Length	10m
Telescope outer Diameter	1.2 meters (3.9 ft)
Field of view	1 degree diameter
Angular resolution	0.5 arcsec
Transmitter Frequency	2250 MHz
Receiver Frequency	2071.8 MHz
Pointing Accuracy	30 arcsec
Power	Two 3 panel solar arrays (2350 W) three 40 amp-hour nickel hydrogen batteries

How Does it Observe?

Earth’s atmosphere absorbs most of the X-rays, Being Above this obstacle allows Chandra to analyze spectra of cosmic sources. Four sensitive mirrors which are nested inside each other, focus the energetic X-rays onto a tiny spot (about half as wide as a human hair!) at the end of the optical bench at about 9.2 meters on the focal plane. Here, Electronic detectors generate sharp images that provide information about the X-rays such as Position, number, Energy, and time of arrival.

Chandra's Hardware Components

This Observatory can be divided into its three major parts:

1. Telescope system: This includes a support structure and four nested mirrors (which look like barrels) kept almost parallel to each other and parallel to incoming X-rays for deflecting them into the electronic detectors.  

2. Science instrument: Consists of ACIS(Advanced CCD Imaging Spectrometer), HRC (High Resolution Camera), High Energy Transmission Grating (HETG) Spectrometer, Low Energy Transmission Grating (LETG) Spectrometer. 

3. Spacecraft: This includes 2 different sets of thrusters(One for Propulsion and other for Applying torque), Chandra’s Thermal Control system (Insulators, Heaters, Cooling radiator, Thermostats) and its two solar arrays.

Science Instruments

1. HRC (High-Resolution Camera): HRC is one of the scientific instruments used at focal plane where X-Rays are detected. There are two MCP (Micro Channel Plates) consisting of a cluster of millions of tiny lead-oxide glass tubes (each about 1/8th of a thickness of human hair and 1.2 meters in length). Special coating on the tubes makes it release electrons when X-Rays are struck and these electrons are accelerated down the tube by high voltage releasing even more electrons. The cross grid wires detect this electronic signal and allow astronauts to construct a detailed map of the X-Ray source. 
2. ACIS (Advanced CCD Imaging Spectrometer): It is another focal plane science instrument of Chandra, consisting an array of Charged Coupled Devices (CCD) which is basically a light-sensitive integrated circuit but highly sophisticated version. It can measure the energy of incoming X-Rays and produce images and thus, allowing us to examine the temperature variations across different X-Ray sources such as hot clouds of gas and remnants of supernova explosions.
3. High Resolution Spectrometers (HETG and LETG): This is an assembly of hundreds of gold transmission gratings placed behind the mirrors. These grating diffract the incoming X-Rays where, the change in the direction is proportional to the energy contained within X-Ray. These distinguished X-Ray lines enable analysis of temperature, ionisation and chemical composition of the source.

Fun Facts

• During maneuvers from one target to another, Chandra turns slower than the minute hand on a clock. 

• The mirrors onboard Chandra are so smooth that if they were earth sized, the highest mountains would be 2 meters tall! 

• The electrical power requirement of Chandra is about the same as a hair dryer. 

• Some of the Light Observed by Chandra will have been travelling through space for ten billion years. 

• Chandra is powerful enough to read a stop sign at a distance of twelve miles.