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The filter roll-off has a width of ~13.5 MHz for both modes, thus ~27 MHz of the digitized band is not usable. Please see the bandpass response plots for each modes in the sections below.
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The SDP pipeline may flag strong spectral lines such as the Galactic HI line and masers. Users are advised when converting to MS to only use the ‘static’, ‘data_lost’, and ‘cam’ flags. |
The NE_107M mode
It is designated as NE_107M for ‘narrowband extended’, and This mode has a digitized bandwidth of 107 MHz with 32k channels (with ~13.5 MHz rolloff on either side, giving an effective bandwidth of ~80 MHz – see Figure 1). This gives a channel width of 3.3 kHz or 0.7 km/s at 1.4 GHz. It is being successfully used for the L-band LSPs MHONGOOSE and Fornax.
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Commissioning results
In Figure 2 below we show the results of observations of M83 in both wideband and 107 MHz narrowband mode. The correlator is performing as expected and the expected sensitivity is achieved.
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Users interested in observing hydroxyl lines should note that while the 1665- and 1667-MHz lines can be observed simultaneously, the bandpass response is not wide enough to encompass the 1612 MHz line as well. The centre frequency cannot be adjusted during an observation.
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Commissioning results
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This mode was offered on a ‘shared-risk’ basis during the 2022 Open Call for proposals. No issues have been reported.
Additional tests utilizing the narrow OH maser lines have established that:
The flux of narrow lines can be recovered, even when unresolved at the spectral resolution of the system
There is no dependence on the tuning of the centre frequency of the band