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Dirk Muders Max-Planck-Institut f ür Radioastronomie Bonn. ACS at the Atacama Pathfinder Experiment (APEX). The APEX Project. APEX is a 12m radio telescope located north of the ALMA site on Chajnantor at 5100m - PowerPoint PPT Presentation
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ACS Workshop, ESO Garching, 03/2004
ACS at the Atacama Pathfinder Experiment (APEX)
Dirk MudersMax-Planck-Institutfür Radioastronomie
Bonn
ACS Workshop, ESO Garching, 03/2004
The APEX Project
● APEX is a 12m radio telescope located north of the ALMA site on Chajnantor at 5100m
● APEX is a pathfinder mission aimed at exploring the southern sub-mm sky in preparation for ALMA
● APEX is a collaboration between MPIfR, AIRUB, ESO and OSO
ACS Workshop, ESO Garching, 03/2004
The APEX Project (cont.)
● APEX is a copy of the US ALMA prototype antenna built by VERTEX
● Compared to the ALMA telescope APEX features two additional Nasmyth receiver cabins, an instrument container and a compressor platform
ACS Workshop, ESO Garching, 03/2004
APEX Interfaces
● APEX uses the same vendor-supplied control computers (ACU & PTC) and the same CAN bus interface (ICD 9) like ALMA
● It was thus decided to re-use the ALMA prototype telescope control software (TICS) and most of the corresponding control hardware setup
ACS Workshop, ESO Garching, 03/2004
APEX Instrumentation
● The APEX instrumentation will consist of:
– Bolometer cameras with several hundred pixels (e.g. LABOCA) at λ=1 mm to 350 μm
– Heterodyne receivers (single-pixel and arrays) at ν=230 GHz to 1.5 THz (200 μm)
– Continuum backends
– Auto-Correlators
ACS Workshop, ESO Garching, 03/2004
APEX Status
● APEX has been erected in early 2003
● In September 2003 the telescope control system hard- and software were installed
● Preliminary acceptance tests took place in November 2003
● Currently the pointing is being checked with an optical telescope
ACS Workshop, ESO Garching, 03/2004
ACS Workshop, ESO Garching, 03/2004
Difficulties at 5000m:Low pressureLow oxygen content
Oxygenization
Pressurized HardDriveBox
ACS Workshop, ESO Garching, 03/2004
ACS / TICS at APEX
● APEX is using TICS and thus ACS
● The ACS version in use is determined by TICS (currently ACS 2.0.1)
● We will probably upgrade to ACS 3.0.1 this year if a new (stable) TICS port will be available
ACS Workshop, ESO Garching, 03/2004
ACS / TICS at APEX (cont.)
● TICS provides antenna control (astronomical coordinate tracking, patterns, CAN bus access, etc.) via 4 COBs
● ALMA's timing setup is much more complicated than needed for APEX
● APEX uses GPS & IRIG-B to slave the ABM to TAI and a hardware timing generator for the 48ms Timing Events
ACS Workshop, ESO Garching, 03/2004
APEX Instrument Interfaces
● APEX instrumentation needs to be interfaced to the ACS -> make components
● Many instruments are legacy devices that use a simple ASCII protocol over a socket rather than the CAN bus that ALMA employs
● Thus a socket DevIO implementation is needed
ACS Workshop, ESO Garching, 03/2004
APEX Socket DevIO
● The socket code needs to handle sending and parsing ASCII messages for component properties AND for methods
● It must handle multiplexing and concurrent accesses to the component properties
● The messages are standardized using the SCPI syntax
ACS Workshop, ESO Garching, 03/2004
Socket DevIO Class Diagram
ACS Workshop, ESO Garching, 03/2004
SCPI Syntax
Component sends the device:
[APEX:]<device name>:<property/method name>?
The device replies:
[APEX:]<device name>:<property/method name> <value> \ <ISO 8601 time stamp>
Example:
APEX:SIS345:LO2:MULTI1:backShort2?
APEX:SIS345:LO2:MULTI1:backShort2 2.341 \ 2003-11-05T10:19:38.310+00.00
ACS Workshop, ESO Garching, 03/2004
APEX Instruments IDLs
● The instrument IDLs are kept as generic as possible to be able to re-use them for new instruments of the same kind; only a new CDB entry is needed
● Instruments are implemented via a hierarchical device tree to:
– have one high-level interface for observing
– have low-level interface(s) for engineering
ACS Workshop, ESO Garching, 03/2004
APEX Device HierarchyAPEX:SIS345 apexHFE.idlAPEX:SIS345:CALUNIT apexHFE_HCal.idlAPEX:SIS345:MIXER1 apexHFE_Mixer.idlAPEX:SIS345:MIXER1:COLDAMP apexHFE_ColdAmp.idlAPEX:SIS345:MIXER2 apexHFE_Mixer.idlAPEX:SIS345:MIXER2:COLDAMP apexHFE_ColdAmp.idlAPEX:SIS345:LO1 apexHFE_LO.idlAPEX:SIS345:LO1:GUNN apexHFE_Gunn.idlAPEX:SIS345:LO1:PLL apexHFE_PLL.idlAPEX:SIS345:LO1:MULTI1 apexHFE_Multi.idlAPEX:SIS345:LO1:MULTI2 apexHFE_Multi.idlAPEX:SIS345:LO2 apexHFE_LO.idlAPEX:SIS345:LO2:GUNN apexHFE_Gunn.idlAPEX:SIS345:LO2:PLL apexHFE_PLL.idlAPEX:SIS345:LO2:MULTI1 apexHFE_Multi.idlAPEX:SIS345:LO2:MULTI2 apexHFE_Multi.idl
ACS Workshop, ESO Garching, 03/2004
Code generation● The C++ component code is automatically
generated from the IDLs using a modified version of the “bdsGenerator” from AIRUB
● C++, *.h, xml and xsd files are created
● DevIOUDPSock socket communication code & SCPI commands are automatically added
● Embedded system host name and port are stored in the CDB and read at startup
ACS Workshop, ESO Garching, 03/2004
Serial & GPIB Devices● Many commercial devices use RS232 or
GPIB communication with given commands
● General problem of non-concurrent access -> need to serialize commands
● Demultiplexing is done in the standalone SCPI command parser (CID) which in turn talks to the hardware, i.e. CID is a “driver”
● Socket DevIO is re-used here
ACS Workshop, ESO Garching, 03/2004
CID Setup
ACS Workshop, ESO Garching, 03/2004
Device Emulators
● A simple Python script was developed to emulate socket devices
● The emulator uses the IDLs and sets up all property types automatically
● Simple funtionality such as setting actual to commanded values is included
● Can be extended easily
ACS Workshop, ESO Garching, 03/2004
APEX Control System (APECS)
● For real observations all those components need to be set up and coordinated to perform “scans”. This is done by the “APEX Observing Engine”
● The APEX raw data format (MBFITS) was defined based on ALMA's TI-FITS
● The raw data writer collects telescope and backend data to write MBFITS files
ACS Workshop, ESO Garching, 03/2004
APECS (cont.)
● APECS uses ACS to provide the necessary infrastructure to observe with APEX:
– Observer CLI & GUI to set up scans for a number of standard observing modes
– Telescope control (via TICS) & device setup
– Raw data (MBFITS) writing
– Online calibration (TA*) and data reduction for
pointing, focus and skydip
ACS Workshop, ESO Garching, 03/2004
APECS Class Diagram
ACS Workshop, ESO Garching, 03/2004
APECS Deployment
Diagram
ACS Workshop, ESO Garching, 03/2004
ACS Pros
● Hides many CORBA details
● Allows for flexible distributed systems
● Simple deployment reconfiguration
● Component property model is very useful for hardware device implementations
● Remote monitoring and remote observing is easily implemented
ACS Workshop, ESO Garching, 03/2004
ACS Cons
● Steep learning curve; lab staff typically does not want to deal with it directly
● ACS is pretty large; this conflicts with using it in embedded systems
● TCP connections get stuck when parts of the software need to be restarted
● Missing connection to existing lab tools such as LabView
ACS Workshop, ESO Garching, 03/2004
APEX's ACS Wishlist
● Auto-reconnection does not always work but is essential for operations
● Rather get a stable and debugged ACS than new features since ACS is the infrastructure for everything else
● Share IDL and naming structure with other projects to facilitate re-using code