Chapter 1: Chandra X-ray Observatory

The Chandra X-ray Observatory (CXO), which was formerly known as the Advanced X-ray Astrophysics Facility (AXAF), is a space observatory of the Flagship class that was launched by NASA on July 23, 1999, onboard the Space Shuttle Columbia during the Space Transportation System (STS-93) phase of the mission. The extraordinary angular resolution of Chandra's mirrors makes it possible for the telescope to detect X-ray sources that are one hundred times less bright than any other X-ray telescope that has come before it. Because the most majority of X-rays are absorbed by the atmosphere of the Earth, it is impossible to detect them using telescopes that are based on Earth. As a result, space-based telescopes are required in order to perform these observations. Chandra is a satellite that orbits the Earth at a distance of 64 hours, and its mission is still active as of the year 2024.

The Hubble Space Telescope, the Compton Gamma Ray Observatory (1991-2000), and the Spitzer Space Telescope (2003-2020) are all considered to be among the Great Observatories. Chandra is yet another of these observatories. The Indian-American astronomer Subrahmanyan Chandrasekhar, who was awarded the Nobel Prize in Physics, is honored with the naming of the telescope. In spite of the fact that Chandra has a far greater angular resolution and XMM-Newton has a larger spectroscopic throughput, the two telescopes have different design foci. Chandra's mission is comparable to that of the European Space Agency's XMM-Newton satellite, which was initially launched in 1999.

Despite the fact that Chandra still has more than a decade of operational life left, it is being threatened with an early cancellation as a result of a reduction in funding for NASA that will be implemented by the United States Congress in 2024. For X-ray astronomy in the United States, the cancelation has been described as a potential occurrence that may be considered "extinction-level." An effort has been made by a group of astronomers to organize a public outreach project with the goal of obtaining sufficient numbers of American citizens to convince the United States Congress to grant sufficient financing in order to prevent the observatory from being shut down prematurely.

A proposal for the Chandra X-ray Observatory, which was referred to as AXAF at the time, was submitted to NASA by Riccardo Giacconi and Harvey Tananbaum in the year 1976. The subsequent year saw the beginning of preliminary work at the Smithsonian Astrophysical Observatory (SAO) and the Marshall Space Flight Center (MSFC). The telescope is currently being operated for the National Aeronautics and Space Administration (NASA) at the Chandra X-ray Center, which is part of the Center for Astrophysics | Harvard & Smithsonian. The first imaging X-ray telescope, known as Einstein (HEAO-2), was put into orbit by the National Aeronautics and Space Administration in 1978. Throughout the 1980s and 1990s, work for the AXAF project continued to be carried out. In the year 1992, the spaceship underwent a redesign in order to cut expenses. In addition to the elimination of two of the six scientific instruments, four of the twelve mirrors that were planned were also removed. The orbit that was originally planned for AXAF was altered to become an elliptical one, and it will reach one third of the distance to the Moon at its most distant point. Despite the fact that this rendered the Space Shuttle incapable of making any improvements or repairs, it did ensure that the observatory would remain above the radiation belts of the Earth for the most of its orbit. TRW, which is now known as Northrop Grumman Aerospace Systems, was responsible for the assembly and testing of AXAF in Redondo Beach, California.

A contest that was sponsored by NASA in 1998 in which more than 6,000 responses were received from all over the world resulted in the renaming of AXAF to Chandra. The names were suggested by the winners of the contest, Jatila van der Veen and Tyrel Johnson, who were both high school students at the time. They did so in honor of Subrahmanyan Chandrasekhar, an Indian-American astrophysicist who was awarded the Nobel Prize. His work in establishing the maximum mass of white dwarf stars has led to a better understanding of high-energy astronomical phenomena such as neutron stars and black holes. He is well-known for his contributions to this field. It seems fitting that the name Chandra comes from the Sanskrit word for "moon."

The launch of the spacecraft was initially planned to take place in December 1998; however, it was postponed by several months and was finally launched on July 23, 1999, at 04:31 UTC by Space Shuttle Columbia during STS-93. At 11:47 UTC, Cady Coleman arrived from Columbia and deployed Chandra to the United States. At 12:48 UTC, the first stage motor of the Inertial Upper Stage ignited. After a period of 125 seconds of burning and separating, the second stage motor started at 12:51 UTC and burned for 117 seconds. It was the biggest payload that had ever been launched by the shuttle, weighing in at 22,753 kilograms (50,162 pounds). This was due to the fact that the shuttle required a two-stage Inertial Upper Stage booster rocket system in order to take the spacecraft towards its high orbit.

Chandra has been returning data ever since it was first introduced, which was one month ago. With cooperation from the Massachusetts Institute of Technology and Northrop Grumman Space Technology, it is managed by the Space Agency Overseas (SAO) at the Chandra X-ray Center in Cambridge, Massachusetts. Particle damage was sustained by the ACIS CCDs during the early radiation belt passes. At this time, the instrument is withdrawn from the focal plane of the telescope during passes in order to avoid any further damage from occurring.

The Chandra spacecraft was previously estimated to have a lifespan of five years; however, on September 4, 2001, the National Aeronautics and Space Administration (NASA) revised its lifespan to ten years "on the basis of the observatory's remarkable results." Chandra has the potential to live for a significantly longer period of time. According to the findings of a research that was carried out in 2004 at the Chandra X-ray Center, the observatory has the potential to last for at least 15 years. According to the Chandra X-ray Center, it is operational as of the year 2024 and has a forthcoming schedule of observations that will be announced.

After being suggested as the next major X-ray observatory in July 2008, the International X-ray Observatory, which was a collaborative project between the European Space Agency (ESA), the National Aeronautics and Space Administration (NASA), and Japan Aerospace Exploration Agency (JAXA), was ultimately scrapped. In later years, the European Space Agency (ESA) resurrected a scaled-down version of the project and renamed it the Advanced Telescope for High Energy Astrophysics (ATHENA), with the launch date set for 2028.

A gyroscope malfunction caused Chandra to enter safe mode operations on October 10, 2018, as a result of the issue. All of the scientific instruments were found to be safe, according to NASA. In a matter of days, the three-second mistake in data from one gyro was comprehended, and preparations were begun to revive Chandra to its full capacity of operation. The gyroscope that was affected by the problem was put into reserve, and it is in normally functioning condition otherwise.

This decision was made by Congress in March of 2024, and it was to limit funding for NASA and its missions.

This could result in the mission being completed earlier than expected.

Senators made a request to NASA in June 2024, urging them to rethink the changes that were made to Chandra, which was granted.

The study of X-ray astronomy has made significant progress as a result of the data that Chandra has collected. The following are some examples of discoveries that Chandra has made that are supported by his observations:

X-ray telescopes, in contrast to optical telescopes, which have simple aluminized parabolic surfaces (mirrors), typically make use of a Wolter telescope, which is comprised of nested cylindrical paraboloid and hyperboloid surfaces that are coated with iridium or gold. X-ray photons would be absorbed by regular mirror surfaces; therefore, mirrors with a low grazing angle are required in order to accomplish the task of reflecting them. Chandra makes use of four pairs of nested mirrors, along with their support structure, which is referred to as the High Resolution Mirror Assembly (HRMA). The mirror substrate is made of glass that is 2 centimeters thick, and the reflecting surface is coated with iridium that is 33 nanometers thick. The diameters of the mirrors are 65 centimeters, 87 centimeters, 99 kilometers, and 123 centimeters. The thick substrate and very meticulous polishing made it possible to create an optical surface that was extremely accurate. This surface is what is responsible for Chandra's unparalleled resolution, which is between 80 and 95 percent of the incoming X-ray radiation being focussed into a circle that is one arcsecond in diameter. The thickness of the substrate, on the other hand, restricts the proportion of the aperture that is filled, which results in a smaller collecting area in comparison to XMM-Newton.

Chandra is able to maintain continuous observation for up to 55 hours of its 65-hour orbital period thanks to its highly elliptical orbit. Chandra is one of the satellites that orbits the Earth that is the furthest distant from the planet when it is at its most distant orbital position. By following this orbit, it is able to travel beyond the geostationary satellites as well as the outer Van Allen belt's boundaries.

Chandra, which has an...