Explanations and the stand-alone ETC package (python scripts)

There was a bug in calc_obstime.py which affected fainter objects requiring long integrations over ∼1 hour in total. Please use the latest version (20231007 or later if available).

Software

• ETC_20231007.zip

Installation

The WINERED ETC is a collection of Python scripts. They only import standard modulces:
os, sys, math, numpy, argparse, matplotlib.pyplot
Moreover, they are currently designed to work with both Python 2 (by importing print_function from __future__) and Python 3. Just download the package from the link above and uncompress the zip file at an appropriate directory before you try to run the scripts.

Tasks

calc_SN

This tool calculates the S/N for a given pair of the brightness (maybe at multiple wavelengths) and the exposure sequence (integration time, number of exposures, and the nodding pattern).

— Try the online PHP tool of calc_SN.

Example

Input:
$ python3 calc_SN.py WIDE 100 winter 0.6 ABBA 60 4 -j 10 -y 12 -hd -s << EOF
10830,5.0E-8
EOF

Output:
wavelength,flux,SN,frame_sec,nframe,nod_sequence
10305.00,9.050e-08,75,60,4,ABBA
12150.00,3.310e-07,223,60,4,ABBA
10830.00,5.000e-08,60,60,4,ABBA

calc_obstime.py

This script calculates required exposure times to achieve a target S/N and the corresponding observational time for a given brightness (maybe in multiple wavelengths).

— Try the online PHP tool of calc_obstime.

Example

Input:
$ python3 calc_obstime.py HIRES-Y 100 winter 0.6 OS 100 -y 10 -s -hd << EOF
> 10830,2.0E-7
> EOF

Output:
wavelength,flux,SN,obstime_sec,frame_sec,nframe,nod_sequence
10305.00,5.710e-07,100,749,202,2,OS
10830.00,2.000e-07,100,1215,435,2,OS

calc_BB.py

This tool calculates the blackbody spectrum for a given set of effective temperature (Teff), J-band mag, and extinction A(J).

— Try the online PHP tool of calc_BB.

Example

Input:
$ python3 calc_BB.py -m WIDE -t 6000 -s 1000 -j 10 -hd

Output:
wavelength,flux
9100.00,7.2629e-07
10100.00,5.7304e-07
11100.00,4.5380e-07
12100.00,3.6168e-07
13100.00,2.9048e-07

Additional notes

How to give brightness

Both the calc_SN and calc_obstime tasks require the brightness information (in the unit of W/m^3) at specific wavelengths (in the unit of Å). J-band and Y-band magnitudes are converted to the effective wavelengths (12150 Å for J and 10305 Å for Y) and the fluxs for the given magnitudes (zero mag corresponds to 3.31E-3 W/m^3 in J and 5.71E-3 W/m^3 in Y). When you call a stand-alone script from the command line, you can give J and/or Y mags with the options --jmag (-j) and --ymag (-j). Any other brightness at each wavelength should be given as a pair of wavelength λ (Å) and flux f (W/m^3) to the standard input from the command line. Check the examples above. The online tools (calc_SN.php and calc_obstime.php) take only one pair of λ and f from an input form.

Any brightness information at wavelengths other than the range of a given mode will be ignored.
— Note that saying J=0 mag, for example, means simply that your input is 3.31E-3 W/m^3 at 12150Å. It gives no spectral data for other wavelengths (getting such spectral data may be done with calc_BB in the blackbody forms). This means a J-band magnitude could be ingnored when the HIRES-Y mode is selected. Nevertheless, if only a J-band mag is given with the HIRES-Y mode without other brightness information, the zero color Y-J=0 is assumed and the result for the Y-band effective wavelength (10305 Å) will be obtained.

Overheads

calc_obstime adds the following overheads to the sum of exposure times.

• Acquisition — 300 sec
• Readout plus FITS creation— 15 sec multiplied by the number of exposures
• Nodding — 15 sec multuplied by the number of position changes (such as A to B or O to S)

For a standard nodding sequence of ABBA, the overheads include the acquisition, four readouts, and two noddings, making 390 seconds (6.5 minutes).

Default parameters

Back to the ETC home page

Updated on 2023-10-07