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Data reduction and analysis facilities

 

The AAO provides facilities for data reduction both at site and in Epping. At the time of writing, these facilities are based mainly on Digital Equipment Corporation (DEC) VAX machines running the VMS operating system. However the AAO is also following the general move towards UNIX workstations; some of these are already available and more are anticipated. § 9.1 lists the expected hardware available at AAO when this guide becomes available, and shows MicroVAXes of various types clustered and networked to a growing assortment of UNIX workstations. All of this will change significantly during the lifetime of this guide.

All these machines are capable of supporting many users simultaneously and there is rarely any difficulty in finding a terminal in order to use them, though anyone with specific requirements - access to an image display device, or a tape drive, for example - may find that these are heavily used. As with all computer systems, the apparent speed of the machines degrades as they get loaded, and visitors may find it worthwhile to work out of normal hours (observers, of all people, should be used to that).

Visitors from the UK who are used to working with Starlink VAXes will find that the AAO VAXes are set up to resemble Starlink systems as closely as possible. The AAO is not technically a Starlink site, but we maintain very close links with Starlink and aim to run all the Starlink-supplied software. In addition (as far as is practical for sites that have to consider the question of Australian support and maintenance) we try to provide the same peripherals (graphics terminals, image displays, etc.) used by Starlink. This means that the UK visitor can expect to run such data reduction systems as ASPIC, KAPPA, Figaro, DIPSO, SCAR, MONGO, (and increasingly, ADAM, as this slowly becomes the standard Starlink software system) etc., - all the software normally available at their home Starlink site. Any private software which runs on a Starlink machine (so long as it does not make use of any particularly unusual features specific to a given machine, such as a link to a local supercomputer), can also be expected to run on the AAO machines.

IRAF is available on the UNIX machines. All the machines at a given site (including the VAXes) are linked via ethernet and support the standard file transfer protocol FTP, so data can be networked between the various machines. However, as this is written, FTP is the only way to transfer data from the VAXes to the UNIX machines, since the UNIX machines do not yet have 9-track or Exabyte tape drives. The use of the workstations for data reduction is still in its infancy at AAO, and teething troubles are to be expected.

The VAX version of IRAF is available, although it is not much used locally. AIPS is not maintained on the AAO machines, but the Epping laboratory is in the grounds of CSIRO Radiophysics who are major users of AIPS, and some arrangement could probably be made to accommodate any visiting AIPS user.

For the benefit of visitors who want to run their own software on the AAO machines, and who are not Starlink users, it should be enough to say that in principle any program that runs under VMS should run on the AAO VAXes - although anyone with programs that use excessive amounts of disk space or other resources, or which need special privileges to run, will need to negotiate a little with the AAO system staff. In practice, the major stumbling blocks are usually connected with the use of different peripherals, generally for graphics, and programs that depend on a particular device that is not available at AAO may have difficulty producing any useful output.

At the time of writing, the most common AAO graphics terminal is the Pericom (MG100 and MG600), which is a VT200/Tektronix emulator device. The MicroVAXes have Digisolve IKON 1024 by 768 image displays. These image devices are eight bits deep with additional overlay planes. AAO will increasingly move over to the use of X-window display systems. The AAO uses the Graphics Kernel System (GKS 7.2) to access all these devices. GKS is an international graphics standard, and any programs written for this standard, even if normally run on different devices, should be able to use the AAO displays. Programs written for SUNs and DECstations should run on the AAO machines, again so long as they do not expect unusual peripherals or obscure subroutine libraries to be available. The NAG numerical algorithms library is currently available on the VAXes and the Epping SUN.

For data and program transfer, 9-track tape drives (1600 and 6250 bpi) are available at both sites on the VAXes. Visitors who want to bring VAX files to Epping should do so in VMS BACKUP format if possible; failing that, the simplest possible format (fixed length ASCII `card images', preferably) should be used. Data files can be brought in FITS format. It is possible to read TK50 and TK70 cartridge tapes on the MicroVAXes. Exabyte tape drives are also available on the MicroVAXes. The SUNs have 150Mb cartridge tape drives and the DECstations have TK50 cartridge drives. UNIX files should therefore be brought, preferably in `tar' format, on one of these cartridge tapes. Note that at present Exabyte and 9-track tapes cannot be read on the UNIX machines. CD readers are currently available on the Epping SUN and one of the DECstations.



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