Last Update: 6th February 2017
|Rx||Tuning Range (GHz)||LO Frequency Range (GHz)|
This user-specified intermediate frequency (in GHz) is the frequency that the "Tracking Frequency" is down-converted into.
In other words, FIF = Ftrack +/- FLO,
where FIF is the Intermediate Frequency, Ftrack is the Tracking Frequency, FLO is the Local Oscillator Frequency, and the +/- sign is determined from the sideband you chose: + for USB and - for LSB. If you are not sure, please use the values provided below. These values correspond the centre of IF of each receiver.
For a multi-beam receiver, positions of beams rotate on the celestial sphere along time. FOREST equips a rotator in order to avoid a rotation of beams. Since the rotator has a limitation on rotation angle (from -100 degrees to 100 degrees), FOREST users should specify the initial rotation angle.
In order to check whether or when the rotator of FOREST reaches the limitation of rotation angle with the initial rotation angle you specified, please use a python tool the observatory offers "multpa.py". The usage is explained here.
2016-2017 observing season:
Only three initial rotation angles of the rotator are permitted: 0, -90 and +90 degrees. This limitation means that a mapping region of the OTF observation cannot be along the position angle of a target.
The SAM45 spectrometer is a highly flexible FX-type correlator (spectrometer) that allows a maximum of 32 GHz of bandwidth (2GHz, ~1.6GHz effective, x 16 arrays) in 4096 spectral channels.
The arrays are donated A1, A2, ..., A16 in the Device table. SAM 45 consists of 16 arrays, where the resolution of the arrays can be set at 3.81, 7.63, 15.26, 30.52, 61.04, 122.07, 244.14, 488.28 kHz.
The user can either chose
(a) one resolution setting common for all 16 arrays,
(b) two independent resolution setting for 8 arrays as a single set (i.e. subarray mode, see below).
The bandwidth for each resolution setting can be calculated by multiplying the number of channels (4096) for each array (see table).
FOREST, TZ, T70, Z45, H40, and H22 receivers can be connected to SAM45.
The following observing modes are available;
(1) OTF with FOREST, TZ1, T70, and H22,
(2) Position switching (single point, random points) with TZ1, T70, Z45, H40, and H22,
(3) Pointing observations with TZ1, T70, Z45, H40, and H22
(4) On-On observations with TZ1 and TZ2.
|Subarray||Subarray 1||Subarray 2|
|Spectral Resolution (kHz)||Bandwidth (MHz)|
This sets the value of the attenuator when the hot load is inserted.
This is typically set to the Y-factor values.
The relationship between Tsys and Y-factor for R-Sky calibration system is roughly as follows:
Tsys = 300 /(10Y/10-1) [K]
This should be adjusted each array if Tsys are varied. These values should be readjusted if Tsys are varied. If you are not sure, please use the following table as a guideline.
|Rx||Frequency (GHz)||Att (dB)|
The role of this "Att"enuator: A value specified at the attenuator (Att) is added to the initial value of the attenuator in the IF system, only when the receiver sees a hot load during the intensity calibration. This additional attenuation reduces the power of a signal to stay in the good linearity range of the system. An inappropriate value specified at the attenuator may cause incorrect values of Tsys and intensities of spectral lines.
This section illustrates how the 2nd Local Oscillator frequency (the 2nd LO frequency) is calculated. The 2nd LO frequency is used to down-convert again the user specified IF frequency into a lower frequency. In most cases, users do not need to take care of the 2nd LO because it is automatically calculated and checked whether it is within a valid range. However, sometimes the observatory asks users to adjust the 2nd LO frequency by themselves. Users can consult the calculated 2nd LO frequency based on the Device Table by pushing the Update button in the Summary Tab.
Step 1: Calculate the following value which is useful for the derivation of the 2nd LO frequency, F2LO.
FdiffIF = Fcentre - Ftrack +/- FIF,
where Fcentre, Ftrack, and FIF are the Center Frequency, the Tracking Frequency, and the Intermediate Frequency, respectively. +/- signs correspond the sideband (+ for USB and - for LSB).
Step 2: Derive the 2nd LO frequency. Choose an appropriate equation based on the receiver and the sideband which the user intend to use.
The observatory provides large numbers of sample files according to the following naming rules:
Screenshots of each sample file and their concrete meanings are shown on the following page.
List of Sample Files of Device Table
When you make an observation script for pointing observations, the observatory recommends using the sample device file named "40u4". This sample table uses H40 receiver and 4 arrays of SAM 45 which is designed to observe SiO(1-0) maser. (If you do not have a specific reason, it is enough to use just 4 arrays of SAM 45 for achieving the purpose of checking and correcting the pointing accuracy of the antenna.)Scroll Back To Top
Click the "Check" button for a basic check of the parameters. This feature only checks for simple typos and it is not meant for checking the details of the observational setup.Scroll Back To Top
Click the "Save" button for saving the device table. Note that this process does not save the main obstable. The user should click the Save button on the Files tab for saving the main obstable script.Scroll Back To Top