CHEOPS
CHEOPS-INAF-MA-MIN-004
Issue: 1 Revision: 0 Page: 1
9. Feb. 2016
Telescope Team meeting
Characterizing ExOPlanet Satellite
(CHEOPS)
CHEOPS-INAF-MA-MIN-004
Issue 1 Revision 0
CHEOPS-IT Telecon Minutes
Telescope Team meeting
Mandatory Cover Page Attributes:
Document Title:
Telescope Team meeting
Origin Name:
INAF: Valentina Viotto, Isabella Pagano
Date of Telecon:
13 May 2013
Table of Contents
1
PARTICIPANTS ........................................................................................................................................... 2
2
IMPORTANT AGENDA ITEMS ..................................................................................................................... 2
3
DECISIONS ................................................................................................................................................. 2
4
OPEN ISSUES ............................................................................................................................................. 5
5
ACTION ITEMS ........................................................................................................................................... 6
6
NEXT MEETING .......................................................................................................................................... 8
CHEOPS
Telescope Team meeting
1
CHEOPS-INAF-MA-MIN-004
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9. Feb. 2016
Instruction for the meeting
Meeting is at Padova Astronomical Observatory, Sala della Madonna, start h 9
2
Participants
Invited: Telescope Team, DPI
Present: RRa, JFa, MMu, DMa, VVi, MDi, DPi, IPa (telecon)
3
Important agenda items

Discuss the CHEOPS Product Tree of interest to the Italian activity

Discuss opto-mechanical interfaces

Draft integration concept to identify requirements on the mounting design

Define needs and responsibilities for breadboard activities
4
Presentations
NA
5
Reference Documents
RD1: CIS-PT and CIS-WBS proposed by Udo Wehmeier on May 3 2013:
http://www.oact.inaf.it/twikicheops/pub/Main/TelescopeManagment/WBS_instruct_v3a.pdf
6
Communications
6.1
Materials adopted for the mechanical parts
DPI provides information on materials adopted for the mechanical parts
 Tube in Carbon Fiber CTE~0.3 ppm/K
 Cells + spider in Invar CTE~1ppm/K
 Primary and secondary mirrors substrate Zerodur CTE~0.001ppm/K
 Carbon fiber  20/30K variation allowed to keep a relative distance variation
between mirrors of ~10microns  Integration can take place at normal room
temperature (20deg)
CHEOPS
Telescope Team meeting
6.2
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Typical tolerances
DPI provides information on typical tolerances
o
o
Carbon fiber:
 T: CTE 0.3ppm/K, deltaT=20K  2.4micron~3micron/320mm~2”
 Settling: a 10/15 micron for each interface
 Outgassing: ~5micron
 M1 decenter 20 micron, axial shift 25 micron, 10”
 M2 30”
 L1, L2 decenter 20micron, axial shift 25micron, 100”
DPi will send preliminary tolerances on the optical bench reference surface and
ranges
7
Decisions
7.1
Project Management
The proposed PT (RD1) is discussed.
The following changes are proposed:
CIS (Cheops Instrument System):
-
OTA (Optical Telescope Assembly):
- OTCC (Optical Train Complete Chain):
CHEOPS
CHEOPS-INAF-MA-MIN-004
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9. Feb. 2016
Telescope Team meeting
Telescope (ITA+UBE): Mirrors, Tube, Spiders, IB-TEL, GSETEL
- BEO (Back-End Optics) (ITA+UBE): BEO optics, BEO
mechanics IB-BEO, GSE-BEO
- Optical Bench (UBE)
- D-BOX: FPA, Detector, FEE, ROE
- Radiators
- Structure
- GSE-OTA
BCA (Baffle and Cover Assembly)
BEE (Back-End Electronics)
-
-
IPA will discuss with UWE and CBR about the feasibility of such changes.
7.2
TELESCOPE
After discussion we agree on:
a. References for alignment OTA wrt spacecraft: Reference spheres + laser tracking
(lateral adjustment) and retro-reflector (angular adjustment);
b. Internal telescope alignment baseline to be given in 4 weeks (mid June);
c. The optical bench is assumed as reference plane;
7.3
BEO
After discussion we agree on:
a. Doublets will be mounted together by the lens manufacturer.
b. Folding mirror: it is under ITA responsibility. The glass and the first interface with the
INVAR support is under ITA responsibility, while the mechanism for tip-tilting is under
UBE responsibility. The interface will be agreed upon the two parts with an interface
between two INVAR metallic parts.
7.4
Integration concept
a. The optical bench is assumed as reference plane: first carbon fiber sheet to which
BEO, TEL and FPA are fixed. A retro-reflector can be introduced to align BCA to the
optical bench, a source producing a fast focal beam can be used to align the FPA.
b. A first integration and alignment procedure for the TEL+BEO, including the use of a
rotation bearing, will be devised in the next 4 weeks.
7.5
Breadboard (BB)
c. A breadboard could be realized with manipulators, which are now foreseen for the
mirrors alignment. The time slot would be second half of 2014. DPi is in favor of
making this exercise (it’s quite easy to do in terms of mechanics thanks to the split of
the manufacturing between UBE and Ruag), moreover the BB could have a larger
application, becoming a breadboard to be used for the FPA integration test, for a
couple of months. Then it will come back to Italy for PFM integration in 2015. The
STM will be used to mechanically and thermally qualify the structure, therefore the
idea would be to replicate the STM (which is flight-design). The only difference would
be in the required carbon fiber CTE (because of time issues). In this case it will not
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Telescope Team meeting
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9. Feb. 2016
be thermally equivalent (no cryo-vacuum test can be carried on). A list of verification
to be done on the breadboard should be produced (INAF). Among these:
 Alignment precision
 Interfaces
 Accessibility
 GSEs
 Integration concept
 Optics adjustment:
o M1: only tilt
o M2: tilt, decenter, axial shift
o detector: tilt, decenter (0.5mm), axial shift
o folding mirror: only tilt
o lenses: tilt, axial shift
7.6
Baffle
a. Already considered coating is ok with carbon fiber.
7.7
Shutter
a. At the moment it’s not baseline
8
Open Issues
8.1
Telescope
8.1.1 Secondary mirror interface to its mount
At the moment the proposed concept consists in an external manipulator (MGSE) to hold the
mirror mount during the alignment, to be then removed after mount fixing to the spiders.
 Question: Glue to fix the alignment? RR is not in favor of that…
 Proposal: a further interface between the part glued to the mirror and the manipulator
has been proposed in order to not introduce a 3-parts responsibility (UBE, ITA, Industry).
The glass and the first interface with the INVAR support is under ITA responsibility, while
the mechanism for tip-tilting is under UBE responsibility. The interface will be agreed
upon the two parts with an interface between two INVAR metallic parts.
8.1.2 Primary mirror interface to its mount

DPi proposal: 3 points attachment (glass-invar) at 120 degrees. The invar cylinders are
then glued (filling the play) to the external part of the mount, which is fixed to the optical
bench reference plane. Metal blades act as compensators for differential movements. A
manipulator must be designed (either fixed on the pads or placed on the back of the
mirror).
Question: Is the stress due to this attachment points negligible wrt defocused PSF or will
it introduce trefoil aberration (for example)?
a) IN CASE, would it be possible to explore other solutions?
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Telescope Team meeting

b) Proposal: insert a further invar interface between the invar pads and the glass,
similar to the one designed for Plato lenses. Of course the weight increases… An
investigation on this topic will be carried on \by DPi.
c) If the latest proposal will be agreed then the glass and the first interface with the
INVAR support will be under ITA responsibility, while the mechanism for tip-tilting will
be under UBE responsibility. The interface will be agreed upon the two parts with an
interface between two INVAR metallic parts.
Question: how do we center the mirror wrt the reference plate?
a) On the specifications of the primary mirror an additional requirement on the
tolerances on the outer edges with respect to the nominal optical axis will be
indicated after negotiation with the proper supplier, and a proper play will be added in
the mounting system to account for such discrepancy.
8.2
BEO
a. Proposal: if all the lenses can stay together on one side of the folding mirror, we’d like to
ask the manufacturer to co-align all the lenses to a common structure.
1. BUT: last lens was expected to act as a defocus compensator
2. BUT: better not to have tip-tilt mirror integrated with the lenses by the manufacturer
to have it free for alignment adjustment
3. Final decision: the lenses MUST be aligned during the telescope AIV.
b. If required, it’s possible to shift the FPA in both axial directions of few tenths of mm, and
also to move it from the optical bench of, again, some centimeters, to fit the optical
design. DPi have been asked to try to give a “volume”, but the final DLR design is not
ready. A feedback on the existing optical designs can be given. DMa will send them to
DPi.
8.3
Baffle
a. Maximum volume? Launcher is not frozen yet, the common free envelope is known at
the moment, but it’s quite small. Iterate with CSL.
b. Internal baffles (IB) size/thickness? IBs confirmed during last meeting in Bern, but a
simulation to estimate the impact of the direct illumination of the trapped focal plane by
the annulus on the sky will be carried on by MMu.
c. An increasing of about 15mm on the interface BCA diameter is required (365mm total)
9
Action Items
Action
WHAT
AI1.
Discuss with UWE and IPA
CBR the proposed
variation of the PT
AI2.
Verify the axial shift of DMA
the focal plane in the
optical design in the
transition between air
and vacuum (DMa)
WHO
DEADLINE
15.5.2013
STATUS
In progress
CHEOPS
Telescope Team meeting
AI3.
Estimate the impact of MMU
the direct illumination of
the trapped focal plane
by the annulus on the
sky and comparison
with the residual Sun
contribution
AI4.
Produce a list of test to VVI
be
done
on
the
breadboard
AI5.
Send the tolerances DPI
(tilt+decenter)
according to which the
TEL+BEO shall be
aligned wrt the optical
bench
AI6.
Send the current optical DMA
designs in step format
to DPi
AI7.
Once
received
the DPI
optical designs, check if
they are compliant with
the
free
envelope
behind
the
optical
bench, on the FPA side
AI8.
Devise
a
first VVI
integration
and
alignment procedure for
the TEL+BEO in the
next 4 weeks, in order
to identify possible
changes
on
the
mechanics
AI9.
Investigate
the DPI
possibility to insert a
further invar interface
between the invar pads
and the glass of the
primary mirror (similar
to the one designed for
Plato lenses).
AI10.
Introduce
a
further DPI
interface between the
invar pad glued to the
secondary mirror and
the manipulator in order
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9. Feb. 2016
CHEOPS
CHEOPS-INAF-MA-MIN-004
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9. Feb. 2016
Telescope Team meeting
to not introduce a 3-part
responsibility
(UBE,
ITA, Industry)
10
Next meeting
tbd
11
Acronyms
OTA
Optical telescope Assembly
PMP
Project Management Plan
PO
Project Office
PRR
Preliminary Requirement Review
12
RF1)
Reference Document
PMP: https://docman.unibe.ch/share/s/ELgp-05gQVqc9Pepyp96ig
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