-------------------------------------------------------------- 1-Introduction Recently, Sivaramakrishnan et al (ISR NICMOS 00-001/005) have produced an updated version of the NICMOS-ETC, which uses the expected instrument performance under NCS. Imaging is the only capability implemented. The program runs from the web as a CGI application at http://picard.stsci.edu/ETC/html/img_etc.html This NICMOS-ETC version will be the starting reference for the JAVA implementation of NICMOS in the APT-ETC (Astronomer's Proposal Tool - Exposure Time Calculator). 2- High level requirements (in priority order) 2.1 Mantain the functionality of the current NICMOS-ETC in imaging mode, adding the explicitly mentioned upgrades/corrections (see below). 2.2 Extend the NICMOS-ETC to the coronographic mode. 2.3 Extend the NICMOS-ETC to the spectroscopic mode. 3- Upgrades/corrections to the current ETC (imaging mode) 3.1 Functional 3.1.1 - Calculations should be done assuming a compromise value of 25e- for the readout noise. It must be comtemplated further refinements of this approach. 3.1.2 - For point sources the user must be able to select the aperture size (e.g. 1x1, 3x3, 5x5,....25x25, 51x51, 101x101 pixels). Default aperture value for each camera should be also included (5x5 for NIC1 3x3 for NIC2, and 1x1 for NIC3). 3.1.3 - The user must be able to select two QE values (average[default], highest). 3.1.4 - Add more choices for the earth shine / zodiacal light (low, average[default], high), and select the proper one depending on the coordinates of the target. 3.1.5 - As an option, the user must be able to include emission lines (given flux, lambda, and width, or EW, lambda, and width) on top of the continuum spectrum. 3.2 Non-functional 4.2.1 - The message "NICMOS IMAGE MODE IN USE" must appear in the window and in the output data file. 3.2.2 Clarify the definition of Signal and Noise for point sources. 3.2.3 - As in the existing ETC, give list of the input values and assumptions, including the readout noise value and sky background. 3.2.4 - Aware that cosmic ray reject implies a reduction of the effective exposure time (or S/N). 3.2.5 - Remove grims from the filter selection. 3.2.6 - The user should not be able to select simultaneously inconsistent fields. (e.g. select the magnitudes for extended objects if the point source option has been selected; filters for NIC2 if NIC1 has selected, etc). 3.2.7 - Explain what 'Source counts (e per s total)' means for point and extended sources. 3.2.8 - Remove the three lines mentioning the standard apertures. (These are not used in the current calculations). 3.2.9 - Specify in the user interface how a 'constant' and a 'power law' spectra are defined (Fnu or Flambda ?). 3.2.10 - Include warnings if: * Non difraction limited observations for point sources: -NIC1 + filter/lambda < 1 micron -NIC2 + filter/lambda < 1.75 microns -NIC3 , always * any polarizer filter selected --> the fractional polarization assumed for the source = 1. * NIC1 + POLS120 --> Consider using POL0S and roll the telescope. 4- Extension to the Coronographic mode - The ETC shall support a Coronographic imaging mode, which is distinct from the standard Imaging. The requirements here follow close those of the ACS. However, a difference with respect to ACS is that in NICMOS the use of the coronographic mode does not imply any additional reduction of the throughput, as the cold mask is always in the beam. 4.1 Functional 4.1.1 - S/N - t calculations for the faint problem object considering as additional noise the flux from the wings of a central bright source (hereafter CS), which is mostly blocked by the spot. 4.1.2 - The spatial distribution of the CS can be approximated by 1-D function. of the distance from the CS. This function is filter dependent. It must be contemplated further refinements for this funtion. 4.1.3 - The calculations must be done for two extreme cases: i) optimal PSF , ii) worst PSF (i.e. spikes, etc). 4.1.4 - The user must be able to specify the separation between the CS and the target (min: 0.3 arcsec, max: 25 arcsec). 4.1.5 - The user must be able to specify the spectrum for the target independently from that of CS. Same choices as in Imaging mode. 4.1.6 - The user must be able to specify the flux (spectrum normalization) for the target independently from that of CS. Same choices as in the imaging mode. 4.1.7 - Same extinction apply to both CS and the target. 4.1.8 - CS will always be a point source. The target can be a point-source or an extended object. As in imaging mode, the S/N- t calculation will proceed 'per pixel' if extended target is selected, and in the area of a square aperture of user-specified size if a point source is selected for the target. 4.2 Non-Functional 4.2.1 - The message "NICMOS CORONOGRAPHIC MODE IN USE" must appear in the window and output data file. 4.2.2 - Only camera NIC 2 (and its corresponding filters) can be selected. 4.2.3 - Following 4.1.3 the message "It is estimated that the current (S/N-t) value is between 'XXX' and 'YYY'" must appear in the window and in the output data file, where 'XXX' and 'YYY' are the results for the best/worst PSFs cases, respectively. 4.2.4 - Similarly to the imaging mode, list of definitions, assumptions, inputs, and warnings, together with the output results. 5- Extension to the spectroscopic mode - The ETC shall support a spectroscopic mode, which is distinct from the standard Imaging. 5.1 Funtional 5.1.1 - Include S/N-t calculations, taking into account that each pixel on the array will receive background radiation over the entire spectral bandpass of the particular grism selected, while the source spectrum will be dispersed over many pixels. 5.1.2 - The user must be able to select one of the three grisms (G096, G141, G206). 5.1.3 - The user must be able to include emission lines (given flux, lambda, and width, or EW, lambda, and width) on top of the continuum spectrum. 5.1.4 - Same input selection for the source as in the imaging mode. 5.2 No functional 5.2.1 - The message "NICMOS SPECTROSCOPIC MODE IN USE" must appear in the window and output data file. 5.2.2 - A message "Intrapixel sensitivity variations may change fluxes by 20%' should be included in the output data file. 5.2.3 - No camera selection (only NIC 3) 5.2.4 - No filter selection. Only 'grism selection' 5.2.5 - Same input selection for the source (an environment) as in the imaging mode. 5.2.6 - Similarly to the imaging mode, list of definitions, assumptions, inputs, and warnings together with the output results. 5.2.7 - Provide a plot of the expected output spectrum. 5.2.8 - Add warning "Extended Source has been selected: The spectra may overlap" if extended source has been selected.