The information on this site is provided for educational, not scientific, purposes. It is kept as up-to-date as possible, but due to the way Chandra is controlled - it is semi-autonomous and we are not in constant contact with it - there is no way to guarantee the current status of Chandra.
The Chandra X-ray Observatory - hereafter Chandra - is one of NASA's four great observatories, the other three being: the Hubble Space Telescope; the Compton Gamma-Ray Observatory; and the Spitzer Space Telescope. It is in orbit around the Earth and taking observations, commanded by the Chandra X-ray Center based on proposals made by professional Astronomers. This site aims to tell you what observation Chandra is performing now, and provide some context for what it is doing.
For science observations, information on the target, the reason for observing the target (the abstract of the proposal), and a variety of views of the target are given. Chandra also regularly performs sets of calibration observations, which are indicated as such, and have no science abstract or imaging data. There are times when Chandra is not taking data, either because the orbit of Chandra is taking it through the radiation belts around Earth - in which case the instruments are moved out of the focal plane of the telescope to prevent radiation damage - or because the telescope has to change its direction to point to a new target. This latter case is known as slewing and for Chandra this is a slow process, since it is a large, heavy, spacecraft and so fast moves would make it harder to obtain the pointing accuracy needed to maximise the high spatial resolution of the telescope. This is in contrast to some missions such as the Swift Gamma-Ray Burst Mission, which is designed to be able to slew very quickly (as it's primary science goal is to observe sources which vary very quickly).
The Tracking Chandra page provides information on Chandra's orbit. The recent trend in placing telescopes into orbit has included a Low-Earth Orbit - such as used by the Hubble Space Telescope and the Suzaku X-ray telescope - and at the L2 point of the Sun-Earth system - such as the Herschel Space Observatory and Gaia. The Chandra orbit is different, in that it is a highly elliptical orbit around the Earth that extends out (at apogee, the furthest point from Earth) to almost one-third the way to the Moon. It takes just over 64 hours to complete one orbit, with only about 15% of the time close to Earth, where the radiation environment is hazardous to the instruments on board (so they are moved out of the focal plane of the telescope to protect them).
The database was last updated on 18:26 Friday, 11 August 2017 (UTC) and contains 15625 scientific observations. The total length of these observations is 11 years and 32 weeks. The observations are from 4123 proposals.
A list of some of the recent changes to the website - useful if a page or link you were using has changed - can be found on the recent changes to the website page.
More information on the Chandra X-ray Observatory can be found on its official home page.
The web site code is available on bitbucket, is coded in Haskell, and runs on the Heroku platform. The version of the code used to create this site can be found on bitbucket at: 93679ada9d09c72e94c988c9fee9d8b4fa7953de.