This viewgraph presentation describes the HERO balloon-borne payload configuration, instrument specifications, flight operations, sensitivity analyses, and future flight plans

Ramsey, Brian D.

Stahl, H. Philip

NASA Technical Reports Server

HERO: A Balloon-Borne Focusing Hard X-Ray Telescope
Brian D. Ramsey and H. Philip Stahl, NASA/Marshall Space Flight Center, Huntsville, Alabama, USA.
The HERO Program
•HERO is an evolutionary balloon payload featuring hard-x-ray focusing optics.
•The optics, focal plane detectors, optical bench, and pointing and aspect systems were all 
designed and fabricated at NASA/MSFC
•The payload utilizes shallow-graze-angle electroformed-nickel replicated optics coated 
with iridium to provide good high energy response. 
•Currently, the payload features 96 mirror shells giving around 80 cm2  of effective 
collecting area up to 45 keV, and more than 40 cm2  up to 60 keV.
•The HERO payload is designed to observe in a relatively unexplored region of the x-ray 
waveband. 
•HERO’s  next flight will be from Alice Spring, Australia in Fall 2009.
Optics Fabrication
HERO Mirror Module (1 of 8)
Figure below shows a single HERO mirror module with 12 
concentrically nested mirror shells
Optics
The HERO instrument consists of 8 optics modules and 8 corresponding focal plane 
detectors, housed in a 6-m-long cylindrical optical bench. The bench is mounted in a 
gondola that provides pointing, power, telemetry and protection.  Below are the details of 
the key instrument components.
7. Electroform Ni
shell on to mandrel
(+)(+) (-)
6. Ultrasonic clean 
and passivation to remove 
surface contaminants
8. Separate optic
from mandrel in
cold water bath
1. CNC machine,
mandrel from 
aluminum bar
2. Chemical clean 
and activation 
& Electroless Nickel 
(EN) plate
3. Precision machine 
to  sub-micron figure
accuracy
4. Polish and
superpolish to
3 -  4Å  rms finish
5. Metrology 
on mandrel
Shell Fabrication
Mandrel Preparation
Item Value
Mirror modules 8
Number of shells per module 12
Focal length 6 m
Inner shell diameter 5 cm
Outer shell diameter 9.4 cm
Shell length (total) 60 cm
Shell thickness 250 μm
Shell material NiCo alloy (75/25)
Prescription Conical approximation to Wolter-1
Shell coating Ir, 60 nm
Resolution (average over 8 modules) 25 arcsec HPD 
System total effective area 80, 40 cm2  (40,60 keV)
Figure below shows the flight mirror modules (with 12 nested shells each) mounted in the 
front of the optical bench. Each module has its own tip/tilt mounting mechanism to permit 
alignment, and Kapton-covered band heaters for thermal control. A protective cap covers 
the assembly in flight.
HERO Flight Operations
The sequence of pictures below shows the HERO balloon payload in  New Mexico. At the top left 
is the gondola in the Columbia Scientific Balloon Facility (CSBF) hangar, undergoing pointing 
tests. To the right of this is the payload on the CSBF launch vehicle, then below are images of 
HERO after launch and during ascent.
Flight Data, May 2007
The figure below shows data obtained during an 1800-sec observation of the Crab Nebula supernova 
remnant (20-60 keV) on May 28, 2007. Approximately 1500 source photons were detected. Some 
residual effects due to telescope motion are still being removed  so that he wings of the source 
extension in the top left to bottom right diagonal plane, the azimuthal  pointing direction for the 
payload, may be slightly exaggerated.    
Future Flight Plans
The next flight of the HERO payload is currently scheduled for September 2009, from Alice 
Springs, Australia. The prime science for this flight will be a high-angular-resolution map of the 
Galactic Center region. Three additional shells will be added to  each module for this flight, 
increasing the payload effective area by about 25%. 
HERO Gondola
The HERO balloon payload, shown below, features a carbon-fiber optical bench and an alt-  
azimuth gyroscopically-controlled pointing system with differential GPS for coarse 
positioning and a pair of day/night star cameras for fine positioning and after-the-fact 
precise attitude reconstruction
The HERO optics, the heart of the instrument, are fabricated at MSFC using an 
electroformed-nickel-replication technique. In this, nickel shells are deposited on a  super-  
polished and figured mandrel, from which they are later released  through differential 
thermal expansion. The figure below shows the steps in the electroforming process.
Item Value
Number of detectors 8
Type Gas scintillation proportional counter
Fill gas Xe/He (96/4) @ 106  pa 
Gas depth 5 cm
Sensitive diameter 5 cm
Readout system Hamamatsu position sensitive 
photomultiplier
Spatial resolution (FWHM) 400 μm (40 keV)
Energy resolution (FWHM) 4% (40 keV)
Efficiency 98% (40keV), 89% (60 keV)
HERO expected sensitivity
The figure below gives the expected sensitivity for the HERO balloon payload in the 
configuration detailed above, assuming a float altitude of 40 km. Data are 5 σ  continuum 
sensitivity (dE/E=0.5), for 3.104  sec observations. A line corresponding to 1 mCrab  (1/1000 
of the Crab Nebula) is also included for comparison
A finished HERO mandrel (left) and a HERO mandrel being polished  (right) 
Multipart plating tank (left) and some finished HERO mirror shells (right
HERO Instrument Specification
Detectors
1.00E-06
1.00E-05
1.00E-04
20 30 40 50 60 70
keV
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HERO mCrab
https://ntrs.nasa.gov/search.jsp?R=20090001895 2019-08-30T05:54:23+00:00Z


HERO: A Balloon-Borne Focusing Hard X-Ray Telescope

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