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Roma

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Sources / Targets / Orbit Target field 60° on the ecliptic Possible sources: Sun, Earth, Moon, ? Satellite in orbit around L2 Max distance form ecliptic ~0.5 Million Km Distances of sources Sun Earth 150 Milllion Km Earth Satellite 1.5 Million Km Moon Satellite 1.12 Million Km Roma, Matteo Munari- INAF OACatania

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Satellite in orbit around L2 Minimal Sources angles from satellite axis Sun 60°Earth 41.6°Moon 35.9° Sources / Targets / Orbit Fiji Islands, 30 Feb 2008Matteo Munari- INAF OACatania

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Lines Of Sight Telescopes field Overlap Roma, Matteo Munari- INAF OACatania Telescope scale ~ 12.5 arcsec/px -> Telescope Field f=24.9° side Configuration Total field side (2-k)f K= overlapping factor K=1 -> 1 LOS ->Total field side =f K=0-> 4 LOS ->Total field side =2f

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Sources angle variation Roma, Matteo Munari- INAF OACatania Sources angles from telescopes axis will vary with the variation of the overlapping factor k and among the telescopes: some of them will be favored by the overlapping mounting, some disfavored ( the telescopes directed toward the source). We consider the disfavored ones to calculate external baffle; the source angles from the telescope axis will be α(s,k)=α(s,0)+f/2(k-1) Where s is the source, f the single telescope field side, k the overlapping factor

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One / Two Stage External Baffle Roma, Matteo Munari- INAF OACatania Two kind of baffle One stage baffle: light from the source is scattered at least once by the baffle and then enters the system. The first lens Of the system sees the baffle Two stage baffle: light form the source is scatterd at least twice; first by a the more external part of baffle (stage two), then by a more internal part (stage one). Stage two is directly illuminated by the source, but is not seen by the first lens of the system; Stage one is seen by the lens, but is not directly illuminated Both kinf of baffle may be emproved by design of vanes that multiplies the scattering, but in a one stage baffle the edge of the vanes are directly seen by the first lens. Obviously, a two stage baffle gives better performances but is bigger! One step baffle Two steps baffle

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One / Two Stage External Baffle Dimensions Roma, Matteo Munari- INAF OACatania One step baffle Two steps baffle Two stages baffle dimensions DB=DL (tan(A)+tan(F))^2/(tan(A)-tan(F))^2 LB=2DL tan(A)/(tan(A)-tan(F))^2 LB2=DL / (tan(A)-tan(F)) DB2=DL (tan(A)+tan(F)/(tan(A)-tan(F)) One stage baffle dimensions DB=DL (tan(A)+tan(F)/(tan(A)-tan(F)) LB=DL /(tan(A)-tan(F)) DL = first lens diameter Α = source angle with telescope axis F= single telescope semi-fov diagonal angle ( fov side / sqrt(2)) DB= Baffle Max Diameter LB=Baffle Total Lenght LB2=Second Stage Length From Lee et al., 2000

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DL=200mm Scale=12.5arcsec/pixel, f=24.9° Source= Sun Roma, Matteo Munari- INAF OACatania One Step Baffle Two Steps Baffle K00.51 DB mm LB mm K00.51 DB mm LB mm LB2 mm

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DL=200mm Scale=12.5arcsec/pixel, f=24.9° Source= Earth Roma, Matteo Munari- INAF OACatania One Step BaffleTwo Steps Baffle K00.51 DB mm LB mm K00.51 DB mm LB mm LB2 mm

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DL=200mm Scale=12.5arcsec/pixel, f=24.9° Source= Moon Roma, Matteo Munari- INAF OACatania One Step Baffle Two Steps Baffle K00.51 DB mm LB mm K00.51 DB mm LB mm LB2 mm

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DL=200mm Scale=15 arcsec/pixel, f=29.9° Source= Sun Roma, Matteo Munari- INAF OACatania One Step Baffle Two Steps Baffle K00.51 DB mm LB mm K00.51 DB mm LB mm LB2 mm

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Single step D=400mm, f=40° From a message of Levacher about next step thermal analysis for the baffle can be allocated a space of 400x400mm Assuming Max Db=400mm FoV (Diag)=40° Dl=200mm We can have Lb~250 (corresponding to max 50° offaxis, enough for Sun with K=0.5) Roma, Matteo Munari- INAF OACatania Single step Db=380mm Lb=168mm Double step Db=723mm Lb=486mm

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SS400mm ABSORBING R0% Roma, Matteo Munari- INAF OACatania

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Roma, Matteo Munari- INAF OACatania SS400mm REFLECTING R5% IN:7.5E-1W OUT:3.3E-2W R=0.044

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SS400mm LAMBERTIAN R5% Roma, Matteo Munari- INAF OACatania IN:5.0E-1W OUT:1.1E-3W R=2.2E-3 IN:7.5E-1W OUT:2.9E-3W R=3.9E-3

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SS400mm REFLECTING R5% Roma, Matteo Munari- INAF OACatania IN:5E-1W OUT:6E-3W R=1.2E-2

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SS400MM LAMBERTIAN R5% Roma, Matteo Munari- INAF OACatania IN:5E-1W OUT:1.6E-3W R=3.2E-3 IN:7.5E-1W OUT:7.5E-5W R=1.0E-4

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SS400mm with vanes Vanes are used so to ensure that the entrance of the system cannot see part of the baffle directly illuminated by the offaxis source Geometrically designed for specular reflection For our baffle 8 vanes Roma, Matteo Munari- INAF OACatania

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SS400MM Vanes Reflective R5% Roma, Matteo Munari- INAF OACatania IN:5E-1W OUT:3.8E-6W R=7.6E-6

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SS400MM Vanes 100% Lambertian R5% Roma, Matteo Munari- INAF OACatania IN:5E-1W OUT:1.8E-5W R=3.6E-5

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SS400MM On Axis Vanes 100% Lambertian R5% Roma, Matteo Munari- INAF OACatania IN:7.5E-1W OUT:4.7E-5W R=6.3E-5

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SS400MM Vanes 50% Lambertian R5% Roma, Matteo Munari- INAF OACatania IN:5E-1W OUT:1.0E-5W R=2.0E-5

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Weights ElementWeight(g) Tube1705 Front60 Edge185 Edge2120 Edge3164 Edge4221 Edge5288 Edge6363 Edge7439 Back509 TOTAL3954 CILINDER2374 CONE1280 Roma, Matteo Munari- INAF OACatania Alluminium (2.7 g/cm3) 2mm thickness

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Issuses/Future work Total assembly of TOUs/satellite Reciprocal Straylight System Sunshield Different baffles for different groups Sources Other sources Impact on duty cycle Materials Paints Baffling system (thermal issues) Specular / Scattering Weight Internal Baffling / StrayLight Mechanics Ghosts Requisites (evaluation method) Roma, Matteo Munari- INAF OACatania

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Roma, Matteo Munari- INAF OACatania

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Roma, Matteo Munari- INAF OACatania

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NOTES Fiji Islands, 30 Feb 2008Mago Merlino - INAF OACamelot What is the role of the sun shield of the satellite? Does it makes an external baffle, for objects lower than the sun on the telescope horizon useless? Aumenting the scale of the telescope will bring at last some source in the fov (is the scale is 20 arcsec/px, for K<~0.6 the Moon could enter in the fov, the Earth for K<~0.35) Other Sources may be present (brilliant objects near the target field, the satellite itself or reciprocal straylight from the telescopes). The calculation here performed refers to the worst case: groupes of telescopes pointing in a more favorable LOS can have a smaller baffle Should be checked how often sources are near the telescopes axis and how this affect the satellite duty cycle Internal baffling system will not impact in telescopes disposition and should have not a great impact on the mass budget

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NOTES Fiji Islands, 30 Feb 2008Mago Merlino - INAF OACamelot The termal baffle and the optical baffle will obviously be the same object. A maximum diameter of 400 mm (as proposed by Levacher for the next step thermal study) means also a trade off between minimun baffled angle overlapping factor and baffling system performances (one or two steps). 400mm could mean K=0, Sun baffled with a single step system K=1, Sun baffled with a double step system K=1, Earth baffled with a single step system

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Preliminary masses Fiji Islands, 30 Feb 2008Mago Merlino - INAF OACamelot Calculated as cilinders of aluminium of 2 mm thickness Vanes are not considered (and consequent growth of dimensions of tube…) -> so this is an Optimistic Estimate! One Step Baffle [g] K00.51 Sun Earth Moon Second Steps Baffle [g] K00.51 Sun Earth Moon1.75 E

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