A wide field spectrograph/camera Roberto Ragazzoni, Carmelo Arcidiacono, Jacopo Farinato, Marco Dima, Emiliano DIolaiti, Giorgia Gentile, Demetrio Magrin Valentina Viotto, Matteo Quasimodo, Fernando Pedichini, Emanuele Giallongo INAF – Padova, Bologna and Roma Observatories October 22 nd , 2008 Sede di Monte Mario
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and balance requirements on the telescope• Precursor experiment? (an off-axis camera)Specific for VLT• How to preserve the VLTI optionSpecific for LBT• Location (fourth bent Nasmith)• Justification & plan for double foci
References• SPIE proc.6272, 25 (2006)• SPIE proc.6269, 187 (2006)• SPIE proc.5492, 121 (2004)• A napkin on a “restaurant” in Copenhagen (2002)
How to go ahead…?• Setting up a consortia or running alone?• VLT, LBT or still keeping the two options open?• Science is probably straightforward but, why not to
“count us”…??? A WorkShop soon on the subject?• A real, INAF endorsed, preliminary design phase, similar
to the one for LBC.
Considerations• This is undoubtely a HUGE projects• Requires a detailed true design to go ahead• Requires to setup a real conosrtium both inside
and outside Italy• Requires connection with data management• One shot is about 1000 x 2kx2k pixels• Requires sort of automatic operations• One spectroscopic shot requires placing a few
thousands slits. It must be automatic to a large extent!
List of issues (preliminary)• VLT vs. LBT issue:• LBT can be trapped or normal Cassegrain. (no way… trapped is by far the
best but just we have to show up this)• In normal Cassegrain there is need of an additional foci position and of a
larger M2 and M3. • Point out masses, sizes involved and feasibility. • In case of VLT arguments about where is the overall cog, and effects on the
interferometry. • About LBT discuss how the two channels can be diversified. • Wavelenght, modalities, number of slits, etc…• Comparison with LSST (2.6deg is the threshold for having the same A
Omega). • How much can be the optical filling factor (dead strips between cameras. • Also recall that due to Cassegrain blurring there is an overlap with
vignetting)• There is a sort of analysis carried out by Giorgia but it is still floating!!!
List of issues (II)
• Optical Design:• Number of lenses. • Goal quality expected to be 80% in
0.3arcsec?? • Mass production of the lenses. • Is there any possibility of inside the FoV
correction to make the single FoV much larger??
• We actually lack a REAL optical design!
List of Issues (III)
• Spectroscopy:• Concept. Review multi fibers just to point out
that is a problem to find out the objects. • Mechanisms, positioning devices. • Preparation to observations.• Where and how to place slits in automatic
manner.• In this moment there are conecpt and fake
movies (even not finished!)
List of issues (IV)• Mechanical design:• Overall design. • Modularity• Accessibility. • Filters exchange• Maintenance• Piping• Overall derotation• Secondary mirror• Can we proceed without a baseline optical design?
Issues (V)• Detectors:• Point out that the area or pixel number is
invariant. Mass production. Quality tes. Certification. Testing? Thinned back illuminated or not? Can me move out from conventional CCD technology?
Issues (VI)• Active Optics:• Just a few modules or additional little cameras for
making ActOpt at a few edges. To be checked/studied• Background:• Just to recall that there could be a background issue.• Data Management:• How much data get out? Picture of the bathroom with a
lot of data everytime you flush it!!!! Yellow claim one do not confgrid all the single images unless requested. Maybe this can be done anyway in a pipeline delayed?
Issues (VII)• International Issues:• VLT and LBT are so different. For LBT Germans claimed
interest and Americans denied it. Competition with LSST. Peculiarity of spectroscopic option.
• Management:• Definition of WPS• Criogenic devices:• Thermal budget. Pletier cooled?• Money:• How much it can really cost? Where can we rob the
money?
Furthermore…
• Science!• We all agree, BUT there is not a well
defined structure• Which must be OUR role?• There will be a meeting somewhere,
hopefully the May 13th, 2008• Will be presented at Ringberg• Will be a poster (sigh…) at Marseille…
First steps
• Define nominal figures• Figure out an optical design• Define a mechanical framework• Setup a scientific environment• Aim to set up the cost!• Still the project need firm and outstanding
documents/papers• Who does what???
Open to free discussion
• What do you think?• Which part do you like?• Which is your opinion into the VLT vs. LBT
issue?• Who we wish to involve into this?• Need to setup a minimum goal with