The Hubble Space Telescope and Next Generation Space Telescope

1
The Hubble Space Telescope and Next Generation
Space Telescope

• Duncan A. Forbes
• Centre for Astrophysics Supercomputing,
  Swinburne University

2
Why a Space Telescope ?

• Putting a telescope in orbit above most of the
  atmosphere has two main advantages
• 1. It is unaffected by seeing (atmospheric
  turbulence) which tends to smear out the detail
  in astronomical objects.
• 2. It can observe at wavelengths which are
  absorbed by the Earths atmosphere e.g. UV and
  infrared wavelengths.

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Hubble Space Telescope Description

• The HST has a 2.4m primary operating at f/24. It
  is in a cyclindrical shape 13.1x4.3m.

The instruments are located in bays behind the
primary mirror. Telescope movement comes from
internal gyros.
HST Schematic
4
How much does it cost ?

• The Hubble Space Telescope was 85 paid for NASA
  and 15 by ESA. Below is a guesstimate how much
  HST cost to develop and maintain.

USmillion Initial Research
and Development 2,000
1st Service mission (inc WFPC2)
500 2nd Service mission (inc STIS,
NICMOS) 600 3rd Service mission
(inc Gyros)
400 Total to date
3,500 Two more missions
are planned to install the ACS (2001) and COS
(2003). Running costs are around US20m/yr.
5
Liftoff of the Space Shuttle Discovery

• On the 24th April 1990, the Space Shuttle
  Discovery blasted off from Cape Canaveral with
  HST onboard.

At an altitude of 600 km (then a record height
for the Shuttle), HST was placed into orbit. The
event was recorded with IMAX cameras. After an
initial systems check the Shuttle returned to
Earth. The first images would be taken later.
Discovery enroute to orbit.
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The Initial Instruments

• HST was launched with 5 instruments.
• WFPC1 Wide Field Planetary Camera 1
• FOC Faint Object Camera
• GHRS Goddard High Resolution Spectrograph
• FOS Faint Object Spectrograph
• HSP High Speed Photometer

HST also included the FGS (Fine Guidance Sensors)
necessary for the acquisition and locking-on to
guide stars.
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Wide Field Planetary Camera 1

• The WFPC1 was designed to be the main imaging
  camera on the HST. It took images over the
  wavelength range 300 to 1000 nm with four CCD
  detectors. Over time the UV sensitivity dropped
  off due to the build-up on contaminants on the
  CCDs.

It could operate in two focal modes f/12.9 or
Wide Field Camera mode, and f/30 Planetary Camera
mode. The resulting pixel scales were 0.1 and
0.043 arcsecs. These were chosen to roughly match
the diffraction limit of the telescope.The total
field-of-views of are 160x160 sq. arcsecs and
64x64 sq. arcsecs respectively.
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Faint Object Camera

• The FOC was built by the European Space Agency.
  Its photocathode and 3-stage intensifier was
  designed to image faint objects.

It had three different focal ratios and therefore
field-of-views and resolution, ie f/48 with
22x22 sq. arcsecs and 0.043 arcsec pixels f/96
with 11x11 sq. arcsecs and 0.022 arcsec
pixels f/288 with 3.6x3.6 sq. arcsecs and 0.0072
arcsec pixels.
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Goddard High Resolution Spectrograph

• Built at Goddard Space Flight Center, the GHRS
  provided high spectral resolution at UV
  wavelengths. It consisted of two 521-channel
  Digicon electronic light detectors. One detector
  was sensitive to light from 105 to 170nm and the
  other from 115 to 320nm.

The GHRS had 3 resolution modes low, medium and
high. If studying the spectrum around 120nm, GHRS
could distinguish two lines that were only 0.06,
0.006 and 0.0012 nm apart for the three modes
respectively.
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Faint Object Spectrograph

• The FOS could obtain spectra of objects that were
  fainter than those possible with the GHRS and
  over a much larger wavelength range (ie 115 to
  800 nm). It consisted of a blue tube sensitive
  from 115 to 550 nm and a red tube covering 180
  to 800 nm. The detectors were two 512-element
  Digicon light intensifiers.

The FOS had various apertures to let the light
through, ranging from 0.1 to 1.0 arcsecs. It had
two spectral resolution modes. It also included
an occulting device to block out the light from
the centre of an object. This was used to block
out the light from a quasar and study the
surrounding host galaxy for example.
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High Speed Photometer

• The HSP was designed to obtain high time
  resolution photometry of astronomical objects,
  for example variable stars, supernovae, active
  galactic nuclei.

As it was the least used of the original
instruments and it was removed when space was
required for the corrective optics (COSTAR). It
was returned to Earth in December 1993.
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STS61

• Lasting almost 11 days, STS61 (launched 2nd Dec.
  1993) was one of the most ambitious shuttle
  missions to be flown.

The astronaunts, which included an astronomer,
had to carefully remove the HSP replace it with
the corrective optics (COSTAR), swap WFPC2 for
WFPC1, and fix the malfunctioning solar arrays.
HST in the cargo bay of Endeavour
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Wide Field Planetary Camera 2

• Although similar to WFPC1, the new WFPC2 had
  several improvements (including internal
  corrective optics), such as better CCD detectors
  and new filters.

WFPC2 consists of 4 separate CCDs. Three (WF
CCDs) are arranged in an L shape with the fourth
(PC) in the bend of the L. The WF CCDs have 0.1
arcsec pixels and 75x75 sq. arcsec field-of-view.
The PC has 0.045 arcsec pixels and 34x34 sq.
arcsec fov. This L shape layout was chosen to
save money.
Schematic layout of the four WFPC2 CCDs.
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Before and After

• Below is an image of M100 taken with WFPC1.

Lets see how it looks with WFPC2, and its
improved optics.
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Astronomy with WFPC2

• WFPC2 is the workhorse imaging camera on HST. Its
  relatively large field-of-view (by HST
  standards), photometric accuracy and spatial
  resolution has made it ideal for imaging distant
  galaxies, gravitational lenses, quasar hosts,
  globular clusters, cepheid variables and
  planetary nebulae to name a few.

Example of a WFPC2 image showing a cluster of
galaxies and several gravitational arcs.
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STS82

• On the 11th Nov. 1997 the Space Shuttle Discovery
  blasted off bound for the HST.

The crew swapped the GHRS and FOC for two new
instruments STIS and NICMOS. They also replaced
a failed FGS, updated the data recorder and
improved the thermal insulation.
Night launch of Discovery
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STIS

• The Space Telescope Imaging Spectrograph can
  obtain 2-dimensional spectra thus it can record
  spectra from many locations in an object
  simultaneously.

It has three detectors a CCD and two MAMAs
(Multi-Anode Mircochannel Arrays). The CCD
operates from 305 to 1000 nm, and the MAMAs from
115 to 170 nm and 165 to 310 nm. The CCD has a
field-of-view of 50x50 sq. arcsec and both MAMAs
have 25x25 sq arcsec.
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Astronomy with STIS

• STIS provides a long slit capability for the
  first time on HST. This has been put to use in
  studying nearby Black Holes in other galaxies.
  STIS can obtain spectra and hence velocities
  either side of the central Black Hole. STIS is
  also the instrument of choice if the astronomer
  wants to observe at UV wavelengths, eg studying
  young hot stars.

The right side figure shows the gas velocities
around a central black hole in M84. Wavelength is
vertical and velocity is horizontal in this
figure. It indicates rapid rotation about the
galaxy nucleus.
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NICMOS

• The Near Infrared Camera and Multi-Object
  Spectrometer can obtain images and spectra at
  wavelengths between 0.8 and 2.5 microns, ie in
  the near infrared. It is cryogenically cooled
  using frozen nitrogen.

It consists of three HgCdTe 256x256 pixel arrays.
These three arrays have different effective pixel
scales, giving a field-of-view of 11x11, 19x19
and 51x51 sq. arcsec.
NICMOS instrument
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Astronomy with NICMOS

• Operating at near-infrared wavelengths means
  NICMOS can penetrate dusty regions. Its main
  limitations are a limited cryogenic lifetime and
  a small field-of-view. Use has focused on imaging
  star formation regions, cores of active galaxies
  and distant galaxies.

Central region of a nearby galaxy imaged by WFPC2
(left) and NICMOS (right).
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Future Instrumentation

• Future HST servicing missions are planned for
  late 2001 (STS109) and 2003. As well as continued
  maintanance, these servicing missions will
  install new instruments.
• Scheduled instruments include the Advanced Camera
  for Surveys (ACS) in 2001, Cosmic Origins
  Spectrograph (COS) in 2003 and possibly the Wide
  Field Camera 3 (WFC3).

It is hoped that HST will remain active and have
at least a few years overlap with the planned 8m
New Generation Space Telescope due for launch
around 2009.
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Advanced Camera for Surveys

• The ACS will become the main imaging camera on
  HST, replacing the WFPC2. It will cover the
  wavelength range from 200 to 1000 nm and from 115
  to 200 nm each with two spatial resolutions.

UV mode will have 0.01 arcsec pixels giving
12.5x12.5 sq arcsecs fov and 0.02 arcsec pixels
giving 50x50 sq arcsec fov. UVred mode will have
0.024 arcsec pixels giving 50x50 sq arcsec fov
and 200x200 sq arcsec fov.
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Cosmic Origins Spectrograph

• The COS is an ultraviolet spectrograph optimized
  to observe faint point-like objects. The
  scientific focus will be quasar absorption lines,
  distant galaxies, horizontal branch stars in
  globular clusters, atmospheres of solar system
  planets.

The instrument will have two channels. A far-UV
channel operating between 115 and 178 nm and a
near-UV one between 178 and 320 nm.
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The Hubble Space Telescope Archive

• Since its launch in 1990, HST has made
• 300,000 observations

of

• 15,000 different objects,

amassing

• 4 Terabytes of data

Essentially all of this data is available to both
professional astronomers and the public alike via
the web-driven interface at http//archive.stsci.e
du
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HST Archive Products
For any requested dataset, the archive provides

• raw data files (uncalibrated data)

• calibrated data files (processed using best
  available bias and flat field calibration
  files)

• data quality files (information about positions
  and characteristics of bad pixels)

• telescope pointing and jitter files (information
  about telescope guiding during observation
  period)

• list of latest and best calibration reference
  files

The calibrated data files are generally
sufficient for most scientific applications. The
HST data handbook describes the pipeline process
and hints for post-pipeline reduction.
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The HST Key Projects

• Three Key Projects
• Quasar Absorption Lines

• Hubble Constant

• Medium Deep Survey

Results published as a series of papers in the
literature.
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HST Imaging Highlights 1990-2000
Scientific highlights from WFPC2 during its first
decade of operation include

• the expansion rate of the Universe

• the deep field

• the birth of stars

• the death of a nearby massive star

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The Hubble Constant
Using Cepheid variables the Hubble constant, and
hence the expansion rate of the Universe, was
measured to an accuracy lt10.
H0 73 /-2random /- 7systematic km/s/Mpc
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The Hubble Deep Field
In 1995, WFPC2 spent 10 consecutive days pointing
at a small patch of sky near the handle of the
Big Dipper.
The resulting image contains over 1500 galaxies,
and represents the deepest astronomical image
ever taken and is one of the most important
contributions to observational cosmology.
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A Stellar Nursery
The spectacular pillars of cool gas and dust in
the Eagle Nebula.
The pillars are being eroded from above by
ultraviolet radiation from massive stars. In
time, hidden embryonic stars within the pillars
will become visible, as the surrounding gas and
dust continues to erode (i.e., photoevaporate).
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Stellar Death Supernova 1987A
The brightest supernova visible from Earth since
Keplers Star of 1604, SN1987A was the result of
an exploding massive star in the Large Magellanic
Cloud.
HST has allowed astronomers to study the early
evolution of a SN at sub-light year scales, for
the first time.
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The Next Generation Space Telescope
Launch 2009 ? Size 8m Cost 1billion
? Wavelengths 0.6 to 30 microns Orbit L2 Web
www.ngst.stsci.edu/science
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Science Drivers Origins

• Structure of the Universe
• Origin and Evolution of Galaxies
• History of the Milky Way
• Birth and Formation of Stars
• Origin of Planetary Systems

Wide-field, diffraction limited imaging in
near-infrared Mid-infrared imaging Spectrograph(s)
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Sensitivity
Factor of 1000 gain over imaging with HSTNICMOS,
factor of 100 gain over GeminiNIRI
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