Next Generation Space Telescope

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• Next Generation Space Telescope
• Status - Spring 2001
• Bob Fosbury (ST-ECF)
• http//www.stecf.org/

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Science goals

• See ?rst-light in the Universe
• Observe the origin evolution of galaxies
• Study structure chemical enrichment of Universe
• Study star and planet formation
• In practice, these goals are represented by the
  Design Reference Mission (DRM)

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The NGST
A collaboration between NASA, ESA and the
Canadian Space Agency (CSA) Observatory launched
to an L2 halo orbit Sun-Earth Lagrangian point,
about 1.5Mkm away Deployable, lightweight
optics Passive cooling gt sunshield
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The instruments

• A near-infrared camera (0.6 5 µm)
• NASA CSA
• A near-infrared multi-object spectrograph (1 5
  µm)
• ESA NASA
• A mid-infrared camera/spectrograph(5 28 µm)
• Europe NASA

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Europes rôle

• Provision of the NIR spectrograph by ESA
• (detectors and MEMS slit-selector supplied by
  NASA)
• European National contributions to the
  mid-infrared instrument (around 50- probably
  optics and bench)
• ESA contributions to the spacecraft
• (details not yet decided)
• ESA support of observatory operations

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Project status

• NASA
• Phase 1 (A/Early B) - 2 prime contractors
• Downselect late 2001
• Technology development programme
• Issue instrument AO mid-2001
• ESA
• F2 selection AWG, SSAC, SPC - late 2000
• Instrument d-studies
• Technology studies
• MIR studies

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NASA re-scope

• Rationale
• Phase A study near completion, 2 validated
  concepts have been studied in detail
• NASA estimates of the cost of each concept exceed
  the available resources
• Mirror technology program has been highly
  successful at demonstrating performance but
  mirror blank preparation and segment polishing
  remain on the critical path - basically, there is
  not enough time to polish 8m aperture
• No time to fly Nexus and learn from it
• Better de-scope now than wait until later

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What to do?

• Follow the ASWG recommended de-scope pathway
• 4. Field
• 3. Spatial resolution
• 2. Number of targets
• 1. Sensitivity
• Maintain First Light in the Universe capability
• Require 1g testability (kill Nexus)
• Reduce dependency on a number of new, high-risk
  technologies
• Enable diversity in launchers and test chambers
• Maintain the approved NASA acquisition strategy

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Recent re-scope exercise

• Increase areal density of mirror from 15 to 20
  kg m-2
• Allows 1g testing
• Reduce aperture from 8 to 6.5m
• Allows launch (mass) and time for polishing
• Heat telescope to 45-50K
• Allows active thermal control

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Performance implications

• Point source
• Around 0.5m in limiting sensitivity
• About a factor 2.3 in exposure time for fixed
  magnitude and s/n
• Due to decreased aperture 8 -gt 6.5m
• Some thermal background added by warm telescope
  above 25µm - roughly another half magnitude in
  limiting sensitivity

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Science review by ISWG

• Whether the capabilities of the revised NGST are
  sufficiently compelling as to warrant the
  projected total cost of the project, particularly
  in the light of what other capabilities will be
  available to astronomers in 2009
• Which science goals are the most important and
  the accomplishment of which should serve as the
  benchmarks for mission success and which should
  be used as guides during the design of the
  mission
• Which science goals should not be mission design
  drivers but are nonetheless sufficiently
  compelling that they should be achieved if at all
  possible
• Which design parameters (e.g., telescope
  diameter, image quality, wavelength coverage,
  pointing and other operational constraints,
  telescope temperature, etc) are likely to have
  the strongest impacts on the science return of
  NGST
• Whether the Design Reference Mission represents
  the scientific usage of NGST appropriately or
  does it need revision in light of the re-scope

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ST-ECF NGST activities

• Current situation and near-term plans
• European NGST activities in 2001
• ESA internal technology development studies
• ESA external studies
• MEMS spectrograph I
• MEMS spectrograph II
• MOS backup
• MIR definition study
• NIRSpec definition
• MISC participation and MIR instrument definition
  study
• SST activities, ISWG support
• Science management planning

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ST-ECF contributions

• ESA/NASA partnership working group (Benvenuti)
• ESA NGST Task Group (Benvenuti - ex-officio)
• ESA NGST Study Science Team (Fosbury)
• NGST US ad hoc Science Working Group - ASWG
  (Fosbury)
• LAS/Dornier ESA-funded spectrograph study
  (Cristiani )
• Laben on-board data management study (Albrecht -
  ex-officio))
• NGST US Interim Science Working Group - ISWG
  (Fosbury - ex-officio)
• ESA F2/3 proposal and Study Report writing
  (Fosbury)
• European NGST science management plan (Fosbury,
  Albrecht)
• European NGST public and community information
  (ST-ECF Newsletter - Fosbury Hubble European
  Space Agency Information Centre - Christensen,
  Benvenuti Euroseminars - various)
• Resigned due to conflict of interest

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Planning for 2001

• Set up European NGST Instrument Science Report
  series
• Red-leak analysis (Cristiani et al.)
• NIRSpec aperture optimisation (Arribas et al.)
• Support current ESA-funded d-studies and SST
  evaluations
• Provide appropriate PR and community information
• Create detailed science management plan for
  European operations
• Create infrastructure for instrument physical
  modelling (based on HST experience)
• Assist ESA in NIRSpec definition by carrying out
  performance studies
• Assist ESA/MISC in MIR by carrying out
  performance studies
• although ECF staff members have little specific
  MIR expertise.

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Long-term planning

• European instrument science activities
• Need to start at instrument definition phase
  (2001)
• Operational support for NGST in general and
  European instruments in particular
• Note that, for the US, NGST is a low-cost
  operation (compared to HST). It will be essential
  for Europe to play an operational role.

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ESA pre-Phase-A studies (199899)

• Telescope Payload Suite
• Contractors Dornier Satellitensysteme, Alcatel
  Space, LAS (Marseilles)
• UK Astronomy Technology Centre (Edinburgh)
• Science Leads Olivier Le Fevre (LAS), Gillian
  Wright (UK-ATC)
• Multi-Object/Integral Field Spectrograph
• Contractors Laboratoire dAstronomie Spatiale
  (Marseille) Dornier
• Satellitensysteme
• w. Durham, ESO, Cambridge, MPE Leiden
• Science Lead Olivier Le Fevre (LAS)
• Visible Wavelength Camera/Spectrograph
• Contractors Matra-Marconi Space
• w. Dornier Satellitensysteme, Leicester, MSSL,
  LAS, UCL Obs. Paris
• Science Lead Martin Ward (Leicester)
• On-Board Data Management
• Contractors Laben w. Dornier Satellitensysteme,
  Istituto di Fisica Cosmica
• (Milan), Arcetri, LAS, Leicester Univ. College
  Dublin
• Science Lead Patrizia Caraveo (IFC)
• Other Spacecraft Subsystems (In-house)

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Current NIRSpec studies

• MEMS-based Near-IR Multi-Object Dispersive
  Spectrograph I (175 kK)
• Contractors Astrium Laboratoire dAstronomie
  Spatiale (Marseille)
• w. Durham, ESO, Cambridge, MPE Leiden
• Science Lead Olivier Le Fevre (LAS)
• MEMS-based Near-IR Multi-Object Dispersive
  Spectrograph II (175 kK)
• Contractors Alcatel Laboratoire dAstronomie
  Spatiale (Marseille)
• Science Lead Denis Burgarella (LAS)
• Alternatives to MEMS for slitmasks for a Near-IR
  Multi-Object Spectrograph (100 kK)
• ITT Issued December 2000
• Closing Date February 23
• Update to Integral Field Spectrograph (75 kK)
• Contractors Laboratoire dAstronomie Spatiale
  (Marseille) Astrium w. Durham, ESO, Cambridge,
  MPE Leiden
• Science Lead Olivier Le Fevre (LAS)

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MEMS developments
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Science operations

• Simpler process than HST
• Different orbit
• Longer observations
• Archive volume is tiny cf. ESO
• Europe will have a direct rôle
• Instrument science for NIRSpec and possibly the
  MIR
• Archiving, User Support, PR etc.