Changes between Initial Version and Version 1 of Diffuser


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Timestamp:
Jul 30, 2021, 7:46:22 AM (16 months ago)
Author:
trac
Comment:

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  • Diffuser

    v1 v1  
     1=== This is where we will collect information and requirements about the diffuser that has been designed to be used with ARCTIC. ===
     2
     3== Project History and Personnel ==
     4
     5The diffuser was funded by a scialog grant from the Research Corporation issued to Suvrath Mahadevan (Penn State), Leslie Hebb (NAPG) and John Wisniewski (OU) :
     6
     7[http://rescorp.org/awards-database/awardee/technologies-and-techniques-for-high-precision-photometric-and-spectroscopi]
     8
     9Joe H’s role was to build the rotator for the diffuser; his time was paid for out of ARC.  Suvrath and his students built the diffuser. Leslie Hebb is now the ARC point of contact for the diffuser.
     10
     11
     12== Science Objective ==
     13
     14A 4" diffuser is placed in front of ARCTIC to spread the light out into a well-defined top-hat PSF.  Looking at a target through the diffuser results in a lot of tiny speckles; the idea was to rotate the diffuser rapidly so that the speckles get blurred out, resulting in improved photometry. ''Do we know what the limiting magnitude of this system is? It was intended to be used on bright stars, but how faint can it go?''
     15
     16See [attachment:Diffuser_20170313.pdf attached presentation] for a presentation of initial performance
     17
     18== Current Specifications ==
     19
     20None known.
     21
     22We should have a handle on the environmental specifications as well. (eg how cold must it operate, specifications on the glass, heat generation of motor, etc)
     23
     24== Commissioning ==
     25
     26The diffuser was commissioned in September 2016, during which test observations of 16 Cyg A & B were conducted.
     27
     28== Preliminary Results ==
     29
     30Brett Morris used it successfully on 1/22/17 and was able to observe a transit of WASP-85.  Based on those preliminary observations (and maybe some others?) it seems likely that the diffuser will enable the observations of transits at a level that is a factor of a few (3?) worse than what Kepler has done - to be able to do this from the ground is very appealing.  The ability to fully characterize the performance of the diffuser has been hampered by bad weather on most of the observing nights during which it was scheduled to be used.
     31
     32== Rotator Issues ==
     33
     34[Non rotator issue, but required engineering just the same: had to replace bearing with a precision bearing - done by Bill]
     35
     36''Need a description of the various issues here.  This is what I can recall...''
     37* Leslie tried to observe with it on 2/5/17 - nothing appeared out of the ordinary but they discovered it was not rotating; Candace was able to rotate it by hand but when commanded it to rotate, no sound of air being pumped through the lines
     38* Candace tested it again on 2/7/17 and the diffuser stopped rotating.  Bill got it working that day but it was clear that it was going to bind again.
     39* Bill tested it again on 2/9/17 and it ran for 30 minutes without issue.
     40* part of the diffuser sent to Jason at UW on 2/11/17 after Leslie was scheduled to use it (without rotation) on the night of 2/10/17
     41* Leslie joined tech-o-con on 2/23/17 to discuss diffuser rotator issue
     42* Jason 3-D printed a new static mount that mounts the diffuser to ARCTIC (made a copy without the bearing and motor); shipped back to APO; ready for operations (in non-rotating mode) on 3/8/17
     43* rotator and bearing assembly stayed at UW; Jason to devise a test bench once the rotator/motor specs are defined
     44
     45
     46== Rotator Solutions ==
     47
     48''Need to collect a set of requirements and then we can explore what would be involved to implement them.''
     49
     50* Rotation and other Performance Specifications ('''here are some notional specs suggested by Mark - ''need to get science drivers from Leslie'' ''')
     51  * Target speed 10 rev/sec , no regulation beyond min/max
     52  * Minimum speed 5 revs/sec, maximum speed 15 revs/sec
     53  * Need indicator of status (if diffuser is in or not) in TUI
     54  * Need indicator of rotation state (rotating or not) in TUI
     55  * Operation temp range -10 deg F to 90 deg F
     56  * dust and moth resistant IP65
     57  * oilless
     58  * Less than 5 watt heat dissipation in front of optical path
     59  * Operational 0 to 100% humidity
     60  * Expected MTBF of >10 million revolutions
     61
     62* Control
     63  * TUI control for in  or out plus status display
     64  * Tui control for spin or not plus status display
     65  * No spin if out
     66  * continuous Spin during sequence
     67  * Start spin 1 sec before first exposure
     68  * stop spin 1 sec after last exposure readout
     69
     70* Physical Size Constraints
     71  * Get from Bill?
     72
     73* Motor Types
     74  * Ed Leon has already begun looking at this.  See his recommendations below in the Attachments section.
     75
     76* Estimated Costs
     77   * TBD
     78   * what have we already spent so far?