Description of the payload

The instrument, is the first one aimed to obtain focused images of astronomical X-ray sources at hard X-ray energies (20-45 keV).

The key component (the hard X-ray optics) are full-shell electroformed-nickel-replicated (ENR) mirrors coated with iridium to enhance high-energy reflectivity. As the critical grazing angle for reflection varies approximately inversely with energy, these mirrors employ smaller angles than their low-energy counterparts and consequently have smaller diameters and collecting areas per shell. The mirrors have a 6 meter focal length.

To exploit the full potential of the HERO optics necessitates a balloon gondola that can provide commensurate pointing accuracy, stability, and pointing knowledge. The HERO gondola utilizes a coarse aspect system for slewing based on a differential global positioning system (GPS) and a fine inertial-mode pointing system that uses a novel day/night aspect camera system to update onboard gyroscopes.

Details of the balloon flight and scientific outcome

Launch site: Scientific Flight Balloon Facility, New Mexico, US  
Balloon launched by: National Scientific Balloon Facility (NSBF)
Balloon manufacturer/size/composition: Zero Pressure Balloon Raven - 39.570.000 cu ft - 0.8 Mil. - SF3-39.57-.8/.8/.8-NA
Balloon serial number: W39.57-2-23
Flight identification number: 497N

The balloon was launched by dynamic method assisted by launch vehicle on May 23, 2001.

The balloon flight spent 17 hr at a float altitude of 39 km during the day and 37 km at night.

During this flight -a test one-, the hard X-ray telescopes were pointed at the Crab Nebula, Cyg X-1, and GRS 1915+105, where they captured the First high-energy focused images of cosmic sources. This test flight confirmed the stability of the optical bench and the ability of the attitude control system to hold X-ray targets with suficient stability for extended periods of time.

External references and bibliographical sources

Images of the mission

View of the HERO optics in a ground test View of the flight line minutes before the launch Balloon release The gondola being picked up by the balloon and released by the launch vehicle View of the initial phase of ascent