Transcript ECF_UC_NGST_Dec01

NGST support at the ST-ECF
Bob Fosbury
http://www.stecf.org/~rfosbury
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ST–ECF UC, Dec 01
NGST@ECF
Current activities
Science oversight: ISWG (NASA), SST (ESA)
Performance studies
Simulations
PR
Future plans
Support of European instrument procurement process
Provision of ESA contribution to Science Operations
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ESA-NASA top level schedule
Activity
2000 2001
2002 2003 2004 2005 2006
2007 2008 2009
NASA
Phase 1 (A/Early B)
Phase 2 (Late B/C/D)
Single Prime Select
Instrument AO Release
Instrument Selection
PDR/NAR
CDR
Launch
12/01
05/01
09/03 03/04
02/02
06/09
09/04
ESA
Delta-Studies (NIR)
Technology Developments
MIR Studies
Decision on ESA Contributions
Definition Phase (NIR)
Phase B (NIR)
Phase C/D (NIR)
MIR Instrument Development
Instrument Delivery
ST–ECF UC, Dec 01
12/06
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Current activities
ST-ECF contribution in 2001:
< 2 FTE including instrument science, s/w
engineering and PR
Fosbury, Cristiani & Freudling members of
ESA Study Science Team
Fosbury ex-officio member of ISWG
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Studies
Parasitic light in NGST instruments…
Cristiani, Arnouts & Fosbury, ISR 2001-01, astroph/0106298
Study of slit size optimisation and crowding
effects
Freudling with Arribas (STScI)
“Spoilers” in MEMS-based spectrographs
Cristiani, Pirzkal, Freudling et al.
Coherence and interference effects in multimirror slits: NGST spectral calibration.
Freudling et al.
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Future plans
ESA intends to contribute to NGST Science
Operations.
NASA needs to minimise operational costs by
using ‘community effort’.
ESA, through the ST-DIV, will provide
instrument science, data-flow and user support
components for the European instrument
contributions. It will also carry out PR and
educational activities.
STScI and ST-ECF are currently discussing how
best to distribute this effort.
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Parasitic light effects
‘Uniform’ sky (Zodi or extended continuum
source) background flooding the detector with
the attenuation produced by the off-MEMS
A set of ‘unwanted’ spectra (stars and galaxies) in
the FOV, brighter than the target sources but
attenuated by the off-MEMS — “SPOILERS”
Light scattered from the MEMS structure which
does not directly enter the collimator
Imperfect filter blocking
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Toy model
Direct and
dispersed images
with spoilers
(bright)
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Range from different authors
Exploitable
contrast limit
set by direct
leakage from
PSF wings of
bright
sources
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Simulations
Catalogues based on HST observations of
HDF-S
Simulations performed using selectively
attenuated slitless spectroscopy
methodology developed for ACS (SLIM,
Pirzkal et al.).
Sensitivity and performance based on
current NGST Mission Simulator
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ST–ECF UC, Dec 01
Simulation parameters
R = 1000
12.7h exposure time in 46x1000s integrations
Target continuum sources are typical Ly-break at
z ~ 3-4 with HAB ~ 24.5-25
Emission line objects are Ly-break with added
emission lines corresponding to low metallictiy
HII regions scaled to give a Lya EW of 2000 Å
and a typical HAB ~ 26.5-27
FOV is 3'x3' with pixels of 0.1" = 1800x1800 pixels
The resulting spectra cover 750 pixels with 16
Å/pixel (constant) in the range 1.2 – 2.4 µm
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Direct image
based on
NICMOS
HDF-S
targets
targets and
spoilers
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Targets
no
noise
Spoilers
and
targets
no
noise
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Targets
with
noise
Targets
and
spoilers
with
noise
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Emission
targets —
50% of
sources
have
emission
Emission
targets &
spoilers
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Emission
targets
with
noise
Targets
and
spoilers
with
noise
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R100 simulations
spectra cover 440 pixels
with 100Å/pixel in
the range 0.6 – 5 µm
Typical magnitudes of
the candidates HAB ~
27–28
1/2 of the candidates
with very strong
emission lines
Exposure time is 19.6hr
to get a S/N~10 @
HAB ~ 28
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Targets
and
noise
Spoilers
and
targets
and
noise
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MEMS phase errors
Study of the throughput (flux calibration)
effects produced by phase differences
introduced between adjacent MEMS
mirrors in the NGST focal plane.
Fourier optics methodology (Freudling)
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OTA & mirror errors
Optical layout
Realisations — 1
Efficiency for
randomly
chosen
mirror
parameters
The maximum
tilt is 0.1°,
the
maximum
offset 0.2µm
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