What ESCS is

ESCS is the DISCOS control software flavour produced for the Medicina and Noto radio telescopes. It is a distributed system based on ACS (ALMA Common Software), commanding all the devices of the telescope and allowing the user to perform single-dish observations in the most common modes. As of today, the code actually implemented for the telescopes (i.e. excluding the huge ACS framework) amounts to > 550000 active lines. Even VLBI (or guest-backend) observations partly rely on ESCS, as it must be used to perform the focus selection and the frontend setup.

This guide is meant to help the observer in the use of ESCS, without dealing with the “behind-the-curtains” complex details of the system. This release focuses on single-dish continuum and spectroscopy observations, as the fully integrated backends available on-site are the analog total power one and the XARCOS spectrometer. Since both the hardware and software implementations are continuously updated, this manual will forcibly undergo frequent revisions.

Here follows a simple schematization of the observing system, helpful to visualize all the main devices ESCS deals with and the most important operations it performs. Notice: the features not yet available in this release are shown in brackets.

ESCS overall tasks

Glossary: terms and abbreviations

>:this symbol precedes commands to be given in the operatorInput panel
$:this symbol precedes commands to be given in a system shell
Beam-parking:the antenna points to a fixed Azimuth-Elevation position
Bin:frequency channel
FWHM:Full-Width Half-Maximum
HPBW:Half-Power BeamWidth
MS:Minor Servo system, which includes the subreflector
Nodding (aka “beam switching”):
 it involves two or more feeds. The source is alternatively observed with each of the feeds, so that there is always one feed “on source”
OTF:On-The-Fly acquisition. The antenna moves according to user-defined parameters, scanning the sky at constant speed. Data acquisition is active during the scan
Position switching (aka “on-off”):
 the beam is alternatively pointed to the source (on) and to a properly defined offset position (off)
Preset:mount mode allowing only beam-parking observations, with no pointing model applied
ProgramTrack:mount mode allowing tracking, OTF/raster scans, beam-parking
Raster:acquisition is performed via discrete pointings (in tracking or beam-parking mode), planned to sample a certain path/area on the sky
Section:acquisition stream (aka “logical channel”). E.g.: the 2 feeds of the K-band receiver used with the continuum backend produce 2 feeds x 2 polarisations = 4 sections
Slewing:motion of the antenna when it is going to the target position. Slewing is always performed at maximum speed, with no data acquisition taking place
Temporised commands:
 user-input or schedule commands that are launched to a specific UT time by means of the “@” symbol
Time-tagged commands:
 when commands are not temporised, the philosophy for their execution is asap (as soon as possible), but the system internally schedules them associating each operation to a properly computed time. This is particularly relevant for the positions commanded to the mount, so that the antenna motions take place along a fully controlled path (except in slewing)
TPB:Total Power Backend
Tracking:the antenna points to a target and, if it’s a celestial target, follows its sidereal motion