ALMA-J Site Testing
ALMA-J Site Testing Archive
Last update 2005-01-24

Fourier Transform Spectrometer

    A Fourier transform spectrometer (FTS) covering a frequency range from 150 GHz to 1.6 THz was fabricated at Nobeyama Radio Observatory. It was used at Pampa la Bola (4800 m a.s.l.) in 1997 September and 1998 June.


    SpectrometerOpticsMartin-Puplett interferometer
    Beam diameter75 mm (F1.6)
    Beam width10 deg (FWHM)
    Throughput0.75 cm2 sr
    Scan length(+/-)16.5 mm
    Scan speed15 mm s-1
    Scan time4 s
    Resolution0.3 cm-1 (10 GHz)
    DetectorBolometerInSb bolometer
    Operating temperature3.7 K
    Frequiency range3 - 53 cm-1 (100-1600 GHz)
    Noise equivalent power1x10-12 W Hz-1/2
    CalibrationTemperature calibratorEccosorb AN-74 at LN2 (73 K) and ambient temperature
    Accuracy< 5 K at 100-1000 GHz, and up to 10% in transmission at the 1450-1600 GHz window.
    SystemTotal weight?? kg
    Power consumption?? W

Technical Description

    Figure 1: Schematic drawing (see Matsuo et al. 1998 for detail).



Figure 2: Best atmospheric transmission spectrum taken by the FTS. This figure was taken between 10:19 and 10:33, 1998 June 17 in Chilean local time (UT - 4 hours). The rest frequencies for some atomic and molecular lines of astrophysical interest are also overplotted (see Matsushita et al. 1999, 2000 for detail).

If you have any comments or questions, e-mail to Satoki Matsushita or Hiroshi Matsuo