A FIRI Demonstrator in Antarctica

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A FIRI Demonstratorin Antarctica

• Paolo G. Calisse1,
• Martin Caldwell4, Rob Ivison2, Peter Ade1, Marie
  Laslandes1, Giorgio Savini3, Derek Ward-Thomson1,
  Matt Griffin1
• 1 Cardiff Univ., 2 Edinburgh Univ., 3 UCL, 4RAL
• ARENA meeting Frascati, Italy - 11-15 May 2009

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Summary

• Science case for high angular resolution
  interferometry in the THz
• Double-FT/interferometry in the THz
• Toward a large THz interferometry space-mission
• lab testbeds
• the Antarctic FIRI Demonstrantor
• Clover, the Antarctic lesson

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roadmap

• 2009-10 Lab testbed
• Technology prototype
• 2010-14 Antarctic THz demonstrator
• Pathfinder for future spaceborne mission
• 2025? Space based Interferometer
• ESA/NASA mission

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Mu-FT development plan

• RAL and Cardiff currently developing a laboratory
  Mu-FT testbed to investigate the scientific
  potential and feasibility of THz direct
  detectors interferometry
• This may lead to the development of a space borne
  interferometer (e.g. FIRI)
• An intermediate step could be represented by a
  ground based demonstrator

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Multi-FT interferometry (Otha et al. 2006 2007)

• A Martin Pupplet spectrometer is applied to a
  Michelson interferometer
• imaging, spectroscopy and polarimetry all in one
• direct detectors (large array)
• Wide bandwidth in the Far Infrared/THz range
• Large arrays, Wide field of view
• Large dynamic range single baseline required at
  a single frequency
• If source spectra is flat observations at various
  frequencies can be added

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Inherent Polarimetry capability
Light Collecting Unit
Fourier Interference Unit
I - Q I Q U V U - V
Wiregrid 2
Beamsplitter
Baseline
Detection unit
Wiregrid 1
only 1/2 signal reaches detetors in this
arrangment
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RAL-Cardiff Testbed
2 testbeds at RAL and Cardiff University
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RAL testbed
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Antarctic THz Multi-FT Interferometer

• Assume 100-m baseline
• 2x 2m diameter dishes
• Syderostat for source tracking
• No baseline rotation required
• At 200um resolution 0.5 arcsec
• At 40um resolution 0.1 arcsec
• Sensitivity assumption 2Jy 1sig/1sec
• 12-hr exposures 10 mJy 1sig
• Atmospheric stability will be an issue

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1-sigma sensitivity

• 3 windows centered at 37, 42, 200 um
• Sensitivity 12H
• Chajnantor (1000 um pwv) 55, 300, 750 mJy
• South Pole (250 um pwv) 8.5, 20, 75 mJy
• Dome C (175 um pwv) 5.3, 8, 24 mJy
• Dome A (100 um pwv) 3.7, 5.3, 14 mJy

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Integration time at 200 um
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Epsilon Eridani

• Typical circum-stellar disc is 100-200 AU.
• In Tau or Oph
• angular size1-2 arcsec.
• warm/hot dust in discs detectable and maybe
  imaged

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Disk structure
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Disks and jets
Many models of bipolar outflows and jets. Tracing
magnetic fields into the inner disks will test
these models
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Orion Proplyds

• Masses 0.01-0.5 Msolar
• Detected by SMA/CARMA (Eisner et al 2008)
• Typically 5-10mJy _at_ 1.3mm
• And 20-40 mJy _at_ 800 microns
• Expected 1 10 Jy _at_ 200 microns
• Same disks in Tau/Hya 1Jy _at_1mm
• 10s - 100s of Jys _at_ 200um
• Easy to detect with the Antarctic THz
  interferometer

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Proplyds at 1.3mm
Eisner et al (2008) ApJ, 683, 304
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Herbig Ae/Be stars
HD169142 (2Mo HAe star _at_ 145pc with SMA 1.4
Panic et al 2008)
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Same disk at 7mm
Disk mass 0.1Mo (Dent et al 2006)
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TW Hydra in CO
TWHy disk of 200AU and 0.005Mo at 50pc in CO with
model Qi et al (2004)
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Same disk in mm continuum
Visibility amplitudes from TWHya fluxes of Jy
(Qi et al 2004)
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Site Considerations

• THz interferometry requires outstanding sites
• High resolution imaging, spectrometry and
  polarimetry can theoretically be performed with a
  Mu-FT, but no actual observations done insofar in
  the FIR
• Good logistic support required for direct
  detectors and PTCs
• u-v coverage easier at polar latitude
• A low boundary layer will improve the quality of
  the observations
• Dome A currently our first candidate site - needs
  aknowledgement by Chinese authorities

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Conclusions

• RAL testbed is now acquiring the first spectra
  and will be used mainly to investigate metrology
  problems
• A 2nd testbed is currently under integration at
  Cardiff to investigate Lic, FI and data sampling
  of the Mu-FT technology
• Both testbeds realized at no-cost with lab spares
  components
• A THz interferometer could demonstrate the
  capability of the technology in 5 years and
  support the technical development of a space
  FIRI-like mission
• It must be seeinteresting n as a necessary step
  for a FIRI-like space mission with an science
  case
• No competing instruments proposed or existing
• Overall cost 10-20 M to be spent in 5-10 yrs
• Will require collaborations from other countries
  and institutions

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Clover

• Experiment devoted to CMB B-pol measurements in
  the mm range
• Initially conceived as a collaboration between
  British Institutions and Italian and French
  Partners, based on Dome C
• 4.7 M funde by FTSC (PPARC) in 2004

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Clover at a glance

• Number of mounts 2
• Original site Dome C
• Mount tipe bs over alt over az
• Optics arrangement CRA
• Main mirrors diameter 1.8 m and 1.6 m
• Band Center (GHz) 97, 150, 225
• Number of Single Polarization Detectors 196
• NET (µK sec) 164, 254, 664
• Beam FWHM arcmin 7.5, 5.5, 5.5
• Sky Coverage deg2 1000
• Cl Range 20 to 1000
• Operation Time years 2
• Integration Time years 0.8
• T Sensitivity per 8' pixel µK 0.8
• Q Sensitivity per 8' pixel µK 1.1
• Minimum r 0.03

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Clover status

• Mount, optical assembly, 2 x 150 mK cryostats,
  and detector array (196 detectors), data-analysis
  pipeline and software modelling in advanced stage
  of development and integration in spring 2009
• Site preparation expected to start in June 2009
• Delivery to site of 1st antenna expected Dec
  2010.
• In 2007, Clover requested an additional amount
  for 2.55 M to FTSC to cover.
• Complete AIV
• Implement design changes
• Delays caused by redeployment in Atacama
• 3 years of operation (not covered by original
  funding 0.8 M
• FTSC rated Clover as a medium-high priority
  project like, for example, Herschel and Planck

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Clover is over!

• Additional funding requested since 2007 to STFC
  to cover
• Changes of internal STFC salary budgeting rules
• Additional development expenses
• A lack of formal agreements with IPEV and PNRA
  and consequent diversion to Atacama ended with
• Redesign costs
• Additional operation and infrastructure costs at
  the site (previously covered by Italian and
  French partners)
• Additional salary costs due to consequent delays
• In April 2009 FTSC suddenly cancelled the
  project.
• No scientific/technical reasons after this GB
  exchange rate to Euros increased 50 quotes to
  ESA and ESO previous agency debts).

We are now seeking for partners interested in
exploiting the hardware work completed insofar
for a new, TBD experiment.