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Student Engineering Projects for 2017

WEAVE

WEAVE is the next observing facility being built for the 4.2-m William Hershel Telescope. The facility comprises a new 2-degree field-of-view prime focus corrector with a pick-and-place fibre positioner, a small number of individually deployable integral field units (IFUs), and a large integral field unit.  The IFUs and the MOS fibres can be used to feed a dual-beam spectrograph and the facility is expected to be on-sky by 2018. 

 

Project 1: Focus Translation System PLC Modifications

Background

The new 2-degree field-of-view prime focus corrector, with a Fibre Positioner, will be placed within the top-end assembly of the telescope as shown in the following figure: 

 

 

 

 

The WEAVE top-end assembly (WTA) consists of a mechanical representation of the Fibre Positioner and the Instrument Rotator which is connected to the actual Central Can that will house the Prime Focus Corrector. The WTA will be connected to the telescope top-end ring via eight telescope vanes connected to four Focus Translation Units (FTU); collectively known as the Focus Translation System (FTS). The whole of the top end is designed to move perpendicularly to the plane defined by the four FTUs. The permitted range of movement is small but allows the top end to be refocussed to deal with changes in the position of the corrector optics due to temperature changes and mechanical flexures induced in the structure as the telescope moves in elevation.

Situation

The FTU Control System, which was designed and built by SENER, uses an Allen Bradley PLC to send command signals to the FTU motors:

The individual demand values are provided by the Telescope Control System (TCS); one value for each motor. This means that for each movement of the FTS, four demand values are required to be sent from the TCS to the FTS Control System (FCS). This system works well but places an additional overhead on the TCS, the overhead is primarily concerned with calculating the individual demand values for the motors.

Project

Given that the available processing power of the PLC is greatly underused, it makes sense to move some of the logic, required to calculate the individual values, from the TCS to the FCS. This project will involve the design and delivery of the PLC code required to accept a single focus demand from the TCS, calculate the demand values for the individual motors and apply the required drive signals to the FTS drive system.  In addition to this, a similar process will need to be implemented for the application of the FTS tilt as function telescope elevation.

 

Project 2: Coding the Observation Block Manager

Background

The WEAVE facility is being built to deliver the science for a number of specific surveys and thus needs to work very effectively and efficiently to maximise the scientific return of the instrument.  To that end , as far as practicable, the observations will be automated.  The Observatory Control System (OCS) is one of the nine systems that constitutes WEAVE and is responsible for controlling certain aspects of the WEAVE instrument, carrying out the exposures and creating the data files. Within the OCS, there are a number work packages that are responsible for delivering a specific functionality of the system. The Observation Block Manager (OBM) is one such work package.

Each observation will be converted into an Observation Block (OB) which is essentially a description of all the information required to carry out an exposure. The OBM is responsible for proving the user tools for managing the OBs and making them available so that another part of the OCS can perform the actual observations.

Situation

Survey groups responsible for providing the observations will create hundreds of Observing Blocks at a time and these will have to be managed in a database. The Use Cases for how the OBs will be managed already exists and is summarised in the following UML diagram:


The principal user of the database will be the On-island Survey Management Team (OISMT) and it will need to have access to the database, via a Graphical User Interface, to examine OBs, include new OBs and delete existing ones.  The idea is to provide this application using state-of-the-art software engineering tools.

Project

The application is designed using a client-server architecture. The server side of the application consists of a servlet running under the Apache Tomcat web server and will be developed in Java using the Google Web Toolkit framework (GWT) which is already used with other systems at the WHT. The client side of the application consists of a set of forms running on any web browser and allows the user can interact with the application. It will be developed using Java and later converted into JavaScript by the GWT compiler so that it can run from any web browser. The purpose of this project is to write the code required to convert the design into reality.
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