Exploring the Invisible Universe - Chandra X-ray Telescope

The Chandra X-ray Observatory has three major elements. They are the spacecraft system, the telescope system and the science instruments.

The Spacecraft System

NASA Chandra X-ray telescope will travel one-third of the way to the Moon in its orbit

The spacecraft module contains computers, communication antennas and data recorders to transmit and receive information between the observatory and ground stations. The onboard computers and sensors, with ground-based control center assistance, command and control the vehicle and monitor its health during its expected five-year lifetime.

The spacecraft module also provides rocket propulsion to move and aim the entire observatory, an aspect camera that tells the observatory its position relative to the stars, and a Sun sensor that protects it from excessive light. Electrical power is provided by solar arrays that also charge three nickel-hydrogen batteries that provide backup power.

The Telescope System

At the heart of the telescope system is the High-Resolution Mirror Assembly. Since high-energy X-rays would penetrate a normal mirror, special cylindrical mirrors were created. The two sets of four nested mirrors resemble tubes within tubes. Incoming X-rays graze off the highly polished mirror surfaces and are funneled to the instrument section for detection and study.

The mirrors of the X-ray observatory are the largest of their kind and the smoothest ever created. The largest of the eight mirrors is almost 4 feet in diameter and 3 feet long. Assembled, the mirror group weighs more than 1 ton. The High-Resolution Mirror Assembly is contained in the cylindrical "telescope" portion of the observatory. The entire length of the telescope is covered with reflective multi-layer insulation that assists heating elements inside the unit in keeping a constant internal temperature. By maintaining a precise temperature, the mirrors within the telescope are not subjected to expansion and contraction – thus ensuring greater accuracy in observations.

NASA

The assembled mirrors were tested at NASA’s Marshall Space Flight Center in Huntsville, Alabama Marshall’s world-class X-ray Calibration Facility verified the mirrors’ exceptional accuracy – comparable to the accuracy required to hit a hole-in-one from Los Angeles to San Diego. This achievement allows the observatory to detect objects separated by one-half arc second. This is comparable to reading the letters of a stop sign 12 miles away.