Call for proposals
 Call for Proposal for ASTE
 How to Prepare for ASTE Observing Proposals
 Instrumentation Overview
How to prepare for ASTE observing proposals
February 7, 2020
Here we have several notes before planning and preparing your observing proposals for ASTE. Please carefully read the document below.
1. Targets for observations
We recommend conducting observations at the elevation angles (EL) between 30 deg. and 80 deg. It means that a source with a declination <+37 deg will be a target for ASTE. Pointing accuracy may be significantly degraded for EL < 30 deg or EL > 80deg. See Fig. 1 for the timeelevation diagram in ASTE for various declination angles of sources.
Observations will be done during “night time”. Here we define the night time as follows: from 1 hour later of the sun set, to 2 hours later of the sun rise. Note that frequent pointing/intensity calibrations may be necessary for observations after sun rise, because a rapid change of the ambient temperature after sun rise may cause a significant variation of the telescope performance. We will have no observations during day time due to degradation of the telescope performance.
The night time at the ASTE site is listed in Table 1. See Fig. 2 for the azimuthelevation diagram for several selected standard/calibration sources and the Sun.
Fig.1(a): Time versus elevation angle diagram for sources at Declination = 80, 60, 40, and 20 deg.
Fig.1(b): Time versus elevation angle diagram for sources at Declination = 20, 0, +20, and +40 deg.
Date  Sunset  Sunrise 

2020/07/01  12:00  01:20 
2020/08/01  14:00  03:20 
2020/09/01  16:20  05:00 
Fig.2: Azimuth versus elevation diagram for several selected standard/calibration sources and the Sun.
2. Estimation of observing time
 For position switch observations

 An rms noise level dT_{A}* of the spectrum after integration time t_{integ} is estimated with the following equation:
,
where T_{sys} is the system noise temperature (SSB) in Kelvin, _{spec} is the efficiency of the spectrometer, and df is a spectral resolution in Hz. The value of _{spec} is 0.96 for the WHSF. In addition, the values of a are sqrt(2) for single polarization and 1.0 for sum of both linear polarizations.  For instance, if we make a 60 sec integration with T_{sys} = 400 K (SSB), spectral resolution df = 1.0 MHz = 1.0 * 10^{6} Hz (it corresponds to a velocity resolution dv = 0.87 km/s at f = 345 GHz or lambda = 0.87 mm), and single polarization, the resulting rms noise level will be dT_{A}* = 76 mK in T_{A}* scale.
 Note that this corresponds to 127 mK in T_{MB} scale (if we adopt the main beam efficiency of 0.6 at 345 GHz for ASTE) or a flux density of 6.0 Jy for 22arcsec beam (a typical beam size of ASTE at 345 GHz).
 See Appendix 1 of this document for intensity conversions between antenna/main beam temperatures and flux density.
 With this equation, estimate the required onsource integration time.
 The same amount of time will be spent for OFF point observations to subtract atmospheric emission. Furthermore, slew time of the telescope will also take into account as a overhead. In total, triple the required onsource integration time to estimate the total observing time, including OFF position observations and telescope slew time. For instance, in order to achieve an onsource integration time of 2 hours, you will need 6 hours in total (without other overheads, i.e., time for receiver tuning, pointing calibration, and standard source observation. See below about the estimation of these overheads).
 An rms noise level dT_{A}* of the spectrum after integration time t_{integ} is estimated with the following equation:
 For OnTheFly (OTF) observations

 Please consult with the ASTEOTF web page.
 Please refer results of the latest tool of sensitivity estimation (otfaste.pl) in your technical justification. Note that outputs from the perl script are for single polarization, not dual polarizations.
 Another overheads other than target observations

 Receiver tuning: 510 minutes with a standard remote tuning.
 Pointing calibration observations: To measure and correct the pointing error, pointing observations (cross scan observations of a planet in a continuum observing mode or five point observations of a compact CO source in a spectroscopy mode) will be done every two hours during observations. It takes 1020 minutes. If you are observing at the evening or morning (i.e., a rapid decrease or increase of the ambient temperature occurs), it is highly recommended to make more frequent pointing observations.
 Standard source observations: Galactic bright objects with known line strength will be observed as a standard source. It takes about 1020 minutes, and we recommend to observe a standard source at least once per night.
Appendix
1. Intensity scale conversion from/to antenna temperature to/from flux density
 Antenna temperature, T_{A}*
 T_{A}* is related to the main beam temperature T_{MB} with the following equation: T_{MB} = T_{A}* /η_{MB}, where η_{MB} is the main beam efficiency. In case of ASTE observations, η_{MB} at 350 and 490 GHz are, respectively, 0.6 and 0.45 for night time in winter.
 Main beam temperature, T_{MB}
 T_{MB}, is related to the flux density S as follows: S = 0.0735 λ^{2} θ^{2} T_{MB}, where λ is the observing wavelength in mm and θ is the beam size in arcsec. For instance, 1 K in T_{MB} scale at 345 GHz (or 0.87 mm) with a 22arcsec beam of ASTE corresponds to a flux density of 47 Jy. Similarly, T_{MB} = 13.6 λ^{2} θ^{2 } S, where S is flux density in Jy/beam. For example, If we observe a point source (unresolved with the ASTE 22 arcsec beam at 345 GHz) with a flux density of 1 Jy will be observed as a 21 mK source in T_{MB} scale, and therefore 13 mK in T_{A}* scale in ASTE (adopting the main beam efficiency of 0.6).