In 1990, NASA sent a X-ray telescope into space on Space Shuttle Columbia for the first time to perform observations of galactic and extragalactic objects: What was BBXRT?

In 1990, NASA sent a X-ray telescope into space on Space Shuttle Columbia for the first time to perform observations of galactic and extragalactic objects. The instrument was called the Broad Band X-ray Telescope, or BBXRT. It was launched on December 2, 1990, during the STS-35 mission. The flight was part of NASA's ASTRO-1 astronomy mission. BBXRT was designed to study X-ray sources in the universe across an energy range from 0.3 to 12 keV. The telescope also served as a test of focusing X-ray optics in space. Its observations helped scientists study X-ray sources using an instrument designed for a broad energy range.

In 1990, NASA sent a X-ray telescope into space aboard Columbia

The Broad Band X-ray Telescope was a space telescope developed for X-ray astronomy. NASA launched BBXRT aboard Space Shuttle Columbia on December 2, 1990. The flight was designated STS-35 and was also known as the ASTRO-1 mission. Columbia remained in space from December 2 through December 11, 1990.


BBXRT was included in the ASTRO-1 payload along with ultraviolet astronomy instruments. The mission allowed NASA and scientists to conduct observations of astronomical objects using different parts of the electromagnetic spectrum. The main target of BBXRT was the universe. Its objective was to perform X-ray observations of both galactic and extragalactic objects.

What was the Broad Band X-ray Telescope?

The Broad Band X-ray Telescope, known as BBXRT, was developed to observe X-ray sources from space. X-rays from astronomical sources cannot be studied effectively from the ground because Earth's atmosphere absorbs most cosmic X-rays. A telescope placed above the atmosphere can therefore collect X-ray signals from objects in space.

BBXRT was designed to focus X-rays and measure their energy. It operated across a range of 0.3 to 12 keV. The telescope was also designed with moderate energy resolution. NASA described it as the first focusing X-ray telescope to operate over a broad energy range of 0.3 to 12 keV with moderate energy resolution. The reported energy resolution was about 90 eV at 1 keV and 150 eV at 6 keV.

Why was the BBXRT mission important?

BBXRT was a test of focusing X-ray optics in space. Earlier X-ray astronomy missions had demonstrated the ability to detect X-rays, but focusing them required telescope designs that could work with the way X-rays interact with surfaces.

X-rays cannot normally be reflected by mirrors in the same way as visible light. BBXRT therefore used grazing-incidence reflection. In this arrangement, X-rays approach the reflecting surface at a shallow angle.

The telescope used nested conical thin-foil aluminum reflectors. The reflectors were coated with acrylic lacquer and had vacuum-deposited gold on their surfaces. This design allowed the telescope to collect and focus incoming X-rays.

BBXRT had two co-aligned telescopes

The technical design of BBXRT included two telescopes that were aligned with each other. Each telescope had a diameter of 40 centimeters. Each had a focal length of 3.77 meters. The telescope system also carried detectors designed to measure incoming X-rays. BBXRT used cryogenically cooled silicon-lithium, or Si(Li), solid-state spectrometers. The detectors operated at about 100 K.

Cooling the detectors was part of the instrument design. The detectors measured the energy of incoming X-rays and provided information that scientists could use to study X-ray sources. The combination of focusing optics and energy-sensitive detectors allowed BBXRT to examine X-ray sources across its operating range.

What did BBXRT observe?

BBXRT was designed to observe both galactic and extragalactic X-ray sources. Galactic objects are objects located within the Milky Way. Extragalactic objects are located outside the Milky Way. X-ray sources can include different types of astronomical objects and physical processes. X-ray observations can provide information that cannot be obtained from visible light alone.

BBXRT's broad energy range was important because X-ray sources can produce radiation at different energies. Measuring these energies helps scientists examine the physical conditions associated with the sources. The instrument therefore combined observations of astronomical objects with measurements of their X-ray energy.

The telescope flew with other ASTRO-1 instruments

BBXRT was not the only astronomy instrument carried by Columbia during the STS-35 mission. It was co-mounted with three ultraviolet telescopes as part of the ASTRO-1 payload. The instruments included the Hopkins Ultraviolet Telescope, or HUT, the Wisconsin Ultraviolet Photo-Polarimeter Experiment, or WUPPE, and the Ultraviolet Imaging Telescope, or UIT.

Together, the instruments allowed the ASTRO-1 mission to study astronomical sources using ultraviolet and X-ray observations. The combination gave scientists access to different types of information from the same space mission.

Who developed BBXRT?

The Broad Band X-ray Telescope was designed and built at NASA's Laboratory for High Energy Astrophysics at the NASA Goddard Space Flight Center. Its development focused on creating an X-ray telescope that could operate across a broad energy range while providing moderate energy resolution.

The telescope's design combined thin-foil reflectors, focusing optics and cooled solid-state detectors. The result was an instrument that could perform X-ray observations from the Space Shuttle Columbia while testing an approach to focusing X-rays in space.

Key BBXRT mission facts

• The main details of the mission can be summarized as follows:
• Instrument: Broad Band X-ray Telescope, or BBXRT
• Type: Space telescope
• Launch date: December 2, 1990
• Mission: STS-35, also known as ASTRO-1
• Spacecraft: Space Shuttle Columbia
• Target: Universe
• Objective: X-ray observations of galactic and extragalactic objects
• Energy range: 0.3 to 12 keV
• Energy resolution: About 90 eV at 1 keV and 150 eV at 6 keV
• Telescope design: Two co-aligned telescopes
• Diameter: 40 centimeters for each telescope
• Focal length: 3.77 meters
• Reflectors: Nested conical thin-foil aluminum reflectors
• Reflector coating: Acrylic lacquer and vacuum-deposited gold
• Detectors: Cryogenically cooled Si(Li) solid-state spectrometers
• Detector operating temperature: About 100 K
• Flight period: December 2 to December 11, 1990
• Payload: ASTRO-1
• Development: NASA Goddard Space Flight Center's Laboratory for High Energy Astrophysics

How did BBXRT focus X-rays?

The telescope used grazing-incidence X-ray reflection. In visible-light astronomy, mirrors can reflect light when it strikes their surfaces. X-rays behave differently. They can penetrate or be absorbed by material when they strike a surface directly.

A grazing-incidence design changes the angle at which X-rays meet the reflector. The X-rays travel almost parallel to the surface. This allows them to be reflected and directed toward the detectors.

BBXRT used nested reflectors to collect X-rays. The reflectors were arranged so that incoming X-rays could be directed toward the focal area. The use of gold on the reflector surfaces was part of the optical design. The thin aluminum foils helped reduce the mass of the telescope while providing the surfaces needed for X-ray reflection.

What made BBXRT different from earlier X-ray instruments?

BBXRT combined focusing X-ray optics with a broad operating energy range and energy-sensitive detectors. Its range extended from 0.3 to 12 keV. It also provided moderate energy resolution. This allowed scientists to examine the energy distribution of X-ray sources rather than simply detecting whether X-rays were present.

NASA described BBXRT as the first focusing X-ray telescope operating over a broad energy range of 0.3 to 12 keV with moderate energy resolution.

The mission therefore had both an observational purpose and a technology-testing purpose.

Why does the 1990 mission remain relevant?

The BBXRT mission represents a stage in the development of space-based X-ray astronomy. X-ray observations require instruments that can operate above Earth's atmosphere. They also require optical systems and detectors designed specifically for X-ray radiation.

BBXRT demonstrated a focusing approach while observing sources across a broad energy range. The December 1990 flight also showed how a Space Shuttle mission could carry an astronomy payload designed to study different wavelengths. Its work formed part of the development of X-ray observing technology used in later space astronomy.