SAM45 (Spectral Analysis Machine for the 45-m telescope): for spectroscopic observations

• FX-type correlator
• Process 16 IFs simultaneously
• Input bandwidth: 2 GHz
• Integration time
  • OTF: 0.1 sec or 0.04 sec (dumping time)
  • Position Switch (PoSW): 1.0 sec. x (integer)
  • On-On: 1.0 sec. x (integer)
• References:
  • Kuno, N. et al., “New observing system of the 45-m telescope at Nobeyama Radio Observatory”, General Assembly and Scientific Symposium, 2011 XXXth URSI, JP2-19 (2011) https://ieeexplore.ieee.org/document/6051296/?arnumber=6051296
  • Kamazaki, T. et al., “Digital Spectro-Correlator System for the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array”, Publications of the Astronomical Society of Japan 64, 29 (16pp) (2012). [ADS]

Available Settings without Spectral Window (SpW) mode

• For a set of IF01 – 08 (=SAM45 Sub-Array 1):
  • The number of channels of output spectrum is fixed to 4096.
  • Users can select channel separation (or bandwidth).
  • This is independent from IF09 – 16 (=SAM45 Sub-Array 2)
• For a set of IF09 – 16 (=SAM45 Sub-Array 2):
  • The number of channels of output spectrum is fixed to 4096.
  • Users can select channel separation (or bandwidth).
  • This is independent from IF01 – 08 (=SAM45 Sub-Array 1)

Available Settings with Spectral Window (SpW) mode: FOREST (4-Beams) only

• For a set of IF01 – 08 (=SAM45 Sub-Array 1):
  • Users can set two(2) spectral windows within a 2 – 4 GHz.: spw1, spw2.
  • These are independent from IF-B (=SAM45 Sub-Array 2)
• For a set of IF09 – 16 (=SAM45 Sub-Array 2):
  • Users can set two(2) spectral windows within a 2 – 4 GHz.: spw1, spw2.
  • These are independent from IF-A (=SAM45 Sub-Array 1)
• Each spectral window:
  • The number of channels of output spectrum is fixed to 2048.
  • Users can set channel separation (or bandwidth) and position for each spectral window.

• See also
  • Special Notes for Spectral Window Mode of SAM45 with FOREST in Appendix

Current SAM45 Status (as of 12th February 2021)

The arrays painted in red are currently not available. Green indicates available arrays.

Due to the mechanical reason, when one array of A(2n-1), A(2n), A(2n+15), and A(2n+17) (n: 1~8) is out of order, rest 3 arrays cannot be used either. Spectral Window (SpW) mode is only available for FOREST receiver. If SpW mode is on, users can use SpW2 (array 17~32).

Distribution of IFs to Backend

• Connections between receivers and SAM45 are very complicated.
• Please refer to sample device tables:
  • H22
  • H40
  • Z45
  • H22 & H40 (Simultaneously)
  • H22 & Z45 (Simultaneously)
  • FOREST
    • 4-beam Normal (non-SpW)
    • 4-beam Spectral Window Mode (with SpW)
    • 2-beam On-On Mode
    • 1-beam (Single-beam)
• See also Special Notes for Spectral Window Mode of SAM45 with FOREST in Appendix

Observing Modes

Three(3) observing modes, position switching (PoSW), On-The-Fly (OTF) mapping, and ON-ON, are available. Frequency switching is NOT available. Chopping/wobbing of the sub-reflector is NOT available. Beam switching is NOT available for spectroscopic observations.

• Position switching (PoSW) mode:
  • The target position (ON position) and nearby sky position (OFF position) are alternately observed to subtract atmospheric emission.
  • It is suited for relatively deep observations of a single point or a small number of observing points of a small area of the sky.
• On-The-Fly (OTF) mode:
  • Continuous acquisition of the data during a raster scan of the telescope.
  • It is appropriate for wide area mapping of a (relatively) bright line.
• ON-ON mode (FOREST only):
  • The target position (ON position) is always observed either the Beam-1 or 3 (beam separation is ∼70 arcsec), except an antenna slew time.
  • It is suited for deep observations of a single point.
  • The apparent size of target should be smaller than beam size.
  • See Nakajima et al. 2013, PASP, 125, 252 for detail.

Absolute Intensity Calibration

• Standard Procedure:
  • The observatory provides information on efficiencies.
  • Users are recommended to measure IRR (Image Rejection Ratio): only 2SB receivers
  • Users calibrate their data using the efficiency (all receivers) and the IRR (2SB receivers only).
• Option for Strong Lines:
  • The observatory provides information on standard sources including calibrated intensity (in T_mb scale).
  • Users observe a standard source during their observations.
    • A small mapping observation is recommended in order to reduce the effects of pointing variability.
  • Users calibrate their data using the observed standard source data.

Data Reduction

• PoSW, ON-ON: NEWSTAR / Java NEWSTAR
• OTF : NOSTAR or CASA