Gamma-Ray Astronomy From Balloons

1
Gamma-Ray Astronomy From Balloons

• Jack Tueller
• Balloon Project Scientist

2
Gamma Rays

• Gamma rays are the highest energy photons.
• Gamma rays do not penetrate to the ground.
• Balloons can provide access to all energies gt20
  keV (Hard X-rays and Gamma Rays)

3
What makes suborbital different?

• Different Risk Management Strategy
• the payload is recovered
• re-flights are inexpensive (lt1M for a balloon vs
  gt100M for a rocket)
• Higher Risk is the Best Strategy
• lower cost
• faster migration of new technology
• smaller more focused efforts
• training new workforce

4
Gamma-Ray Astronomy from Balloons

• atmospheric cutoff is 20keV no soft x-rays
• To get a high sensitivity gamma-ray payloads must
  be big and heavy
• gamma-ray payloads work best at low
  latitudes magnetic shielding low
  background
• gamma-ray payloads must be pointed
• real science is possible but we need LDB at low
  latitudes

5
SN1987A

• first nearby supernova in 400 years
• every instrument possible was used
• many new phenomena were discovered

after
before

• balloons can provide quick access to space for
  timely measurements

HST rings
6
High Resolution Spectroscopy

• In 1987 there were no high resolution germanium
  spectrometers in space like INTEGRAL
• Gamma-ray lines yield nuclear yields and velocity
  distribution that cannot be determined at other
  wavelengths
• Balloon experiments filled the gap GRIS,
  HEXAGONE, Lockheed Martin
• balloon's success leads to INTEGRAL

GRIS
INTEGRAL
7
SN1987A Lines

• Gamma ray line profiles are not distorted by
  complicated effects such as resonant scattering.
• Line profiles did not fit the standard
  models.Lines are red-shifted not blue-shifted.
• But, they validate the detailed IR line profiles.
• SN1987a was an asymmetric explosion!
• future 44Ti lines?

8
Nuclear Lines
Boggs ACT Concept Study

• Nuclear lines are the unique signal of the
  production of new elements

9
Type Ia Supernovae
10
Compton Scattering

• GRIS worked with large detectors to capture all
  the energy and a thick collimator (800 lbs of
  NaI) to isolate the source.
• Compton scattering is the dominant cross section
  between 200 keV and 2 MeV where most of the
  interesting gamma ray lines occur.
• Localizing all the interactions allows accurate
  reconstruction of the source positions and
  spectra over a wide field

11
Compton Telescopes

• Development of an Advanced Compton Telescope
• several technologies are possible
• Si Ge strip detectors
• Si CdZnTe strip detectors
• thick Si
• Liquid Xe
• Gaseous Xe-LaBr3
• LaBr3
• All are now or are proposed balloon payloads

ACT Concept
12
High Energy Gamma Rays

• Technology for EGRET developed on HEBE balloon
  experiment
• Go-no go test of GLAST technology on
  balloonsWould the background rejection work?

CGRO/EGRET
balloon test bed
detector
13
Understanding Supermassive Black Holes

• How do black holes form and grow?
• What stops the growth?
• How do black holes effect galaxy formation?

• Only in hard x-ray can you find all the sources
  and measure their luminosity.

14
ProtoEXIST
Swift/BAT Hard X-ray Survey gt14 keV

• A hard X-ray all-sky monitor can make great
  advances in variability studies of black holes.
• A sensitive hard X-ray all-sky survey is the only
  way to find all the obscured sources.

EXIST
15
Hard X-ray Focusing Optics

• multilayer grazing incidence focusing optics
• long focal lengths are required (InFOCuS is 8m)
• CdZnTe focal plane is the other critical
  technology. (A Si focal plane would be 1 cm
  thick.)
• Balloons can accommodate long focal lengths
  without costly mechanisms.

9m
InFOCuS
No mechanism was required to launch 9m truss.
16
3 Balloon Instruments

• Three instruments are currently active
• HEFT-CIT Columbia
• InFOCuS-GSFC Nagoya
• HERO-MSFC
• Each of these instruments test alternative
  technology for hard x-ray focusing optics.
• Proposed for Con-X enhancement and SMEX-NuSTAR

17
The Black Hole at the Galactic Center

• A supermassive black hole lurks at the Galactic
  Center.
• Like most black holes at the center of galaxies
  it is a very weak source at all wavelengths.
• What is the accretion rate and why is it so low?
• The GC is a very crowded area.
• Only high resolution hard X-ray imaging can
  answer this question.

INTEGRAL
INTEGRAL imaging with gt10 arcmin resolution is
hopelessly confused. Soft X-ray imaging with
Chandra sees 2000 sources lt10 arcmin from the
center.
18
What is the future?

• How do we maintain strong balloon science in
  this field?
• long duration flights at low latitude
• super pressure balloon
• trajectory modification system
• long duration requires higher reliability - more
  cost and oversight
• advanced designsbigger and heavier payloads
• secure and adequate funding

19
Workforce Replenishment

• How are future instrument builders recruited and
  trained?
• BALLOONS!
• fast enough for grad student to complete all
  phases of a project
• small enough for the university researcher
• open to hands-on student participation
• pushing newest technology
• produces significant science results

Mission/ Instrument PI
CGRO
BATSE Fishman
EGRET Fichtel
INTEGRAL
SPI Teegarden
Matteson
HEAO-3 Jacobson
HEAO-1 Peterson
20
Conclusions

• Gamma-ray astronomy could have a bright future in
  ballooning.
• Significant science can be achieved on balloons.
• Balloons are crucial to the development of new
  missions.
• Low cost ballooning can keep a field alive in
  hard times.
• Ballooning is the natural way to recruit and
  train a workforce.NASA and gamma-ray astronomy
  need a vigorous balloon program