#!/bin/csh

# mchw  10 sep 2003

echo Calculate PdB sensitivity

# typical winter conditions expected at SMA site

obstau altitude=2.65 freq=100 mmh2o=2
obstau altitude=2.65 freq=230 mmh2o=2
obstau altitude=2.65 freq=345 mmh2o=2

# Get average diameter from total collecting area of 15 antenna SMA array

calc 'sqrt((1*15**2+9*6.1**2)/10)'

# Use aperture efficiency of 75, 55  35% assumed for PdB antennas
# correspnds to 21, 28  and 44 Jy/K  estimated at 345 GHz.
# Lucas private communication
# Ruze loss assuming 60 micron surface
calc 'exp(-(4*pi*0.06/300*100)**2)' = 0.94%
calc 'exp(-(4*pi*0.06/300*230)**2)' = 0.72%
calc 'exp(-(4*pi*0.06/300*345)**2)' = 0.47%

Subject: 
              Re: - correlator specs
        Date: 
              Fri, 19 Sep 2003 10:16:54 +0200
        From: 
              "R. Lucas" <lucas@iram.fr>
- line sensitivity should definitely be dual polarization (the current
correlator does allows this up to 1GHz bandwidth)
- continuum sensitivity should use 4 GHz, dual pol.
Tsys at 345 may be assumed as 350K average (Trec=70K, eta_f = .94, water
1.5mm)

Plateau de Bure has S/T = 28 Jy/K at 230 and we assume 44 at 345 GHz 
(21 at 100 GHz); at 345 GHz this relies on tuning the worst three 
antennas to the average of the best three (need some effort but well
feasible).

ALMA is more theoretical - aperture efficiency is > 0.75 (project book -
Stephane might know better). So taking this value I get 32.5 Jy/K.


- dual polarization receivers with SSB, 4GHz bandwidth. Tsys expected:
150, 230, 350 (at 1.41 air mass) for freqs of 115, 230, 345 GHz

- 4 GHz, dual polarization correlator being studied (detailed
characteristics such as number of channels, units, unknown yet). The
current one has 8 units of 320 MHz, so it covers only 2 times 1GHz. 

- extension of NS baseline to 368m (in progress) and  EW baseline to
792m 

All this is expected to come in a staged process of course, over the
next 3 years or so.


# Continuum sensitivity
obsrms tsys=100 antdiam=15,.75  bw=4000 nants=6 freq=100
obsrms tsys=230 antdiam=15,.55  bw=4000 nants=6 freq=230
obsrms tsys=350 antdiam=15,.35  bw=4000 nants=6 freq=345

# Spectral Line Sensitivity (1 km/s)
obsrms tsys=100 antdiam=15,.75  deltav=1 nants=6 freq=100
obsrms tsys=230 antdiam=15,.55  deltav=1 nants=6 freq=230
obsrms tsys=350 antdiam=15,.35  deltav=1 nants=6 freq=345

