Jeff Apple

First Images from HERO: A Hard-X-Ray Focusing Telescope

We are developing a balloon-borne hard X-ray telescope that utilizes grazing-incidence optics. Termed HERO, for High-Energy Replicated Optics, the instrument will provide unprecedented sensitivity in the hard X-ray region and will achieve millicrab-level sensitivity in a typical 3 hr balloon-flight observation and 50 μcrab sensitivity on ultralong-duration flights. A recent proof-of-concept flight, featuring a small number of mirror shells, captured the first focused hard X-ray images of galactic X-ray sources. Full details of the payload, its expected future performance, and its recent measurements are provided.

Daytime Aspect Camera for Balloon Altitudes

We have designed, built, and flight-tested a new star camera for daytime guiding of pointed balloon-borne experiments at altitudes around 40 km. The camera and lens are commercially available, off-the-shelf components, but require a custom-built baffle to reduce stray light, especially near the sunlit limb of the balloon. This new camera, which operates in the 600- to 1000-nm region of the spectrum, successfully provides daytime aspect information of approx. 10 arcsec resolution for two distinct star fields near the galactic plane. The detected scattered-light backgrounds show good agreement with the Air Force MODTRAN models used to design the camera, but the daytime stellar magnitude limit was lower than expected due to longitudinal chromatic aberration in the lens. Replacing the commercial lens with a custom-built lens should allow the system to track stars in any arbitrary area of the sky during the daytime.

HERO: high-energy replicated optics for a hard-x-ray balloon payload

We are developing high-energy grazing-incidence optics for a balloon-borne hard-x-ray telescope. When completed the instrument, termed HERO for High Energy Replicated Optics, will have 200 cm2 effective collecting area at 40 keV and <EQ 30 arcsec angular resolution. The payload will offer unprecedented sensitivity in the hard-x-ray region, with milliCrab level sensitivity on a one-day balloon flight and 100 microCrab on an ultra-long-duration flight. While the full science payload is scheduled for flight in 2002, an engineering/proving flight is currently awaiting launch. This flight, consisting of just two mirror modules, each containing three nested shells above a pair of gas scintillation proportional counter focal plane detectors, is intended to test a newly designed gondola pointing and aspect system and to examine the stability of optical bench designs. This paper provides an overview of the HERO program.

A large-area microstrip-gas-counter for X-ray astronomy

We have developed a large-area coded-mask telescope for hard-X-ray astronomy. The heart of the instrument is an imaging microstrip-gas-counter of active area 30 cm × 30 cm and filled with 2 × 105 Pa of xenon + 2% isobutylene. Fabricated on a single sheet of borosilicate glass, 1 mm thick, the microstrip features fine anodes (10 μm) and interleaved cathodes from which the position sensing is derived. Rear pickup electrodes provide the second coordinate. Full details of the instrument and its performance are presented. A first flight, from a high-altitude balloon, is scheduled for the Spring of 1997.

The high energy replicated optics to explore the sun mission: a hard x-ray balloon-borne telescope

Set to fly in the Fall of 2013 from Ft. Sumner, NM, the High Energy Replicated Optics to Explore the Sun (HEROES) mission is a collaborative effort between the NASA Marshall Space Flight Center and the Goddard Space Flight Center to upgrade an existing payload, the High Energy Replicated Optics (HERO) balloon-borne telescope, to make unique scientific measurements of the Sun and astrophysical targets during the same flight. The HEROES science payload consists of 8 mirror modules, housing a total of 109 grazing-incidence optics. These modules are mounted on a carbon-fiber and Aluminum optical bench 6 m from a matching array of high pressure xenon gas scintillation proportional counters, which serve as the focal-plane detectors. The HEROES gondola utilizes a differential GPS system (backed by a magnetometer) for coarse pointing in the azimuth and a shaft angle encoder plus inclinometer provides the coarse elevation. The HEROES payload will incorporate a new solar aspect system to supplement the existing star camera, for fine pointing during both the day and night. The overall payload will be discussed as well as the new solar aspect system. This mission is funded by the NASA HOPE (Hands On Project Experience) Training Opportunity awarded by the NASA Academy of Program/Project and Engineering Leadership, in partnership with NASAs Science Mission Directorate, Office of the Chief Engineer and Office of the Chief Technologist.

HERO: program status and first images from a balloon-borne focusing hard x-ray telescope

HERO is a balloon payload featuring shallow-graze angle replicated optics for hard-x-ray imaging. When completed, the instrument will offer unprecedented sensitivity in the hard-x-ray region, giving thousands of sources to choose from for detailed study on long flights. A recent proof-of-concept flight captured the first hard-x-ray focused images of the Crab Nebula, Cygnus X-1 and GRS 1915+105. Full details of the HERO program are presented, including the design and performance of the optics, the detectors and the gondola. Results from the recent proving flight are discussed together with expected future performance when the full science payload is completed.

Marshall Space Flight Center imaging x-ray experiment (MIXE)

The MIXE includes a state-of-the-art imaging proportional counter which utilizes fluorescence gating in order to achieve high sensitivity in the bandwidth from the xenon k-edge (35 keV) to 100 keV. The current detector system includes a parallel amplification stage to allow for improved energy resolution without sacrificing spatial resolution. Another novel feature is the molybdenum/stainless steel pressure vessel, which is an important factor in achieving low background rates. In this paper we compare the results of Monte Carlo simulations with laboratory experiments and present data obtained during a recent balloon flight from Palestine, Texas.

High Energy Replicated Optics to Explore the Sun balloon-borne telescope: Astrophysical pointing

On September 21st, 2013, the High Energy Replicated Optics to Explore the Sun, or HEROES, balloon-borne x-ray telescope launched from the Columbia Scientific Balloon Facilitys site in Ft. Sumner, NM. The flight lasted for ~27 hours and the observational targets included the Sun and astrophysical sources GRS 1915+105 and the Crab Nebula. Over the past year, the HEROES team upgraded the existing High Energy Replicated Optics (HERO) balloon-borne telescope to make unique scientific measurements of the Sun and astrophysical targets during the same flight. The HEROES Project is a multi-NASA Center effort with team members at both Marshall Space Flight Center (MSFC) and Goddard Space Flight Center (GSFC), and is led by Co-PIs (one at each Center). The HEROES payload consists of the hard X-ray telescope HERO, developed at MSFC, combined with several new systems. To allow the HEROES telescope to make observations of the Sun, a new solar aspect system was added to supplement the existing star camera for fine pointing during both the day and night. A mechanical shutter was added to the star camera to protect it during solar observations and two alignment monitoring systems were added for improved pointing and post-flight data reconstruction. This mission was funded by the NASA HOPE (Hands-On Project Experience) Training Opportunity awarded by the NASA Academy of Program/Project and Engineering Leadership, in partnership with NASAs Science Mission Directorate, Office of the Chief Engineer and Office of the Chief Technologist.

A high energy focal-plane gas scintillation proportional counter

We are developing high-pressure gas scintillation proportional counters for the focus of balloon-borne hard-X-ray telescopes as part of our HERO (High-Energy Replicated Optics) program. Each detector has an active diameter of 5 cm, and is filled with a xenon +4% helium mix at a total pressure of 10 ATM. Imaging is via a position-sensitive photomultiplier tube located immediately below a UV transmitting exit window. Two units are currently under construction and evaluation for a night in the spring of 2000. We present details of their design and construction together with data from preliminary X-ray testing.