14 October, 2008
The crane lifting the Front End with precaution
The installation of the Front End is a very delicate operation and follows an intricate procedure to gently lift the 500 kg weight of the equipment (using both a crane and a telehandler) to the receiver cabin and then lifting and aligning the device onto the antenna support structure. Furthermore, all of this must be done without damaging the delicate mirror alignments and electrical and cryogenic components attached to the cryostat.
The device has to be precisely aligned onto the antenna support structure
The ALMA Front End system is the first element in a complex chain of signal receiving, conversion, processing and recording. The ALMA Front End is designed to receive signals of different frequency bands. It is far superior to any existing systems. Indeed, spin offs of the ALMA prototypes are leading to improved sensitivities in existing millimeter and submillimeter observatories around the world.
The Front End units are comprised of numerous elements, produced at different locations in Europe, North America, East Asia and Chile. The Front End installed on ACA #2 was built in North America and has four operating bands (3,6,7,9). Although it is an engineering model (not fully characterized yet), one can demonstrate for the first time the compatibility of the interfaces with the antenna and with the control software.
This critical operation must be done without damaging the delicate mirror alignments and electrical and cryogenic components attached to the cryostat
The Back End Antenna Articles and Amplitude Calibration Device have also been installed on ACA #2. These installations represent a subset of activities required for the full integration of the electronic systems in the antenna which enable scientific operations. “The addition of the Front End is a critical step in establishing the full signal path used by astronomical signals”, states Joseph McMullin, the AIV System Integration Lead.
The ALMA Director (on the left) together with the AIV, NAOJ and Site teams after the successful installation of the Front End in ACA #2