Spectrograph Interface Control

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JHU tasks (no external interfaces)

• Slithead identification (which slithead is installed?) will be sensed and reported by the on-board spectrograph computer. JHU will supply sensing units or machining instructions to UW for the slithead if necessary.

   

• Collimator motions, Hartmann masks, and shutter will be controlled by the on-board computer.

   

• Temperature sensing for instrument configuration will be done by the on-board computer.

   

• Observer's software to handle spectrographic observations will be written by JHU and installed on the Fermilab supplied observatory workstation. This software communicates with most other systems.

University of Washington

• Spectrograph to telescope: JHU will supply UW with spectrograph mounting locations, machining details, and parts.

   

• Slithead to spectrograph: The slithead will be designed jointly by JHU and UW to guarantee correct optical properties and easy insertion into and removal from the spectrograph. UW will fabricate all slitheads, including one test unit for fit-checks and optical alignment in Baltimore.

  UW will be responsible for the slithead latch-down control. JHU will design the slithead clamp and door mechanism, and supply the clamp and door hardware, but UW will supply the control electronics, pneumatic controls, and software. Currently, this means that the spectrographs show one air input that actuates the JHU-supplied pneumatic clamp and two air inputs that control the JHU-supplied actuator for the slithead door (open+close motions). Additional control items (sensors, etc.) will be designed and installed by JHU if requested.

   

• Electric power to the rotator will be handled by UW. The spectrographs need one circuit of 15 amps 115VAC.

   

• Pressurized air to the rotator will be handled by UW. JHU needs one line with 90 psi, oil-free and dry.

   

• Cooling liquid (antifreeze) to the rotator will handled by UW. JHU will consult with UW about plumbing and flow requirements for its equipment.

   

• Telescope control computer: JHU will generate a command list and appropriate responses from the TCC for those commands not already implemented. These commands will be given by the Observer's software running on the observer's workstation.

   

• Serial data link to rotator will be handled by UW. JHU requires at least two lines at 9600 baud or higher, X/ON-X/OFF.

   

• Guide camera will be handled by UW. JHU must be informed about special machining requirements for installation on the spectrograph.

   

• Acquisition and guiding: JHU will move the telescope to the field coordinates by communications to the TCC. The UW guider will acquire, scale, rotate, focus, and lock. UW will provide (via the TCC?) a guider status structure including current photometry (so JHU can build a time series) and position error (rotation and translation). JHU will use this information to predict remaining exposure time and build a jitter map.

   

• Calibration system will be built by UW with consultation with JHU. The white screen will be activated by the Observer's software via a command to the UW TCC. Lamps will be selected by both UW and JHU (JHU will do some lamp testing prior to final selection). Lamps will be activated by a commmand to the TCC.

   

Princeton University

• CCD Dewar bolt pattern and flange dimensions must be agreed upon by JHU and Princeton. Note that all real-time D/A operations related to the CCD are handled by an interface between Fermilab and Princeton.

  Similarly, the liquid nitrogen supply and control is handled by an interface between UW and Princeton, with no JHU involvement. JHU needs to know about plumbing for matters like cable routing, access, etc., however.

   

• Test electronics will be supplied by Princeton in the form of drawings for or an actual prototype board for an IBM-PC/AT. Device driver software as well.

   

• Field flattening optics will be delivered by JHU to Princeton for installation in the CCD dewars.

Fermilab

• Data acquisition system: The observer's software will communicate via ethernet to the D/A system. JHU will generate a command list and appropriate responses for those commands not already implemented.

   

• Database computer at APO: The observer's software will query the observatory database for information on the currently installed fiber cartridge. Returned information should include field coordinates (how to point the telescope for initial setup), the complete fiber-to-object identification map (including information about anomalies: unused fibers, sky fibers, etc.), and text information for the observer.

   

• Observer's workstation will be supplied by Fermilab. JHU will install software and connect hardware (via serial lines) to this machine.

   

• Time will be read from the observatory workstation. This machine should have a clock (+/-1 s or better) synced to an NTP server.

   

University of Chicago

• Data format and contents will be specified by the Spectroscopic Pipeline group. JHU will write software to produce the appropriate format.

   

First draft: May 2, 1994