The Exposure Time Calculators (ETCs) are online tools that predict the count rates and S/N in various observing modes given specified source characteristics.
Use the following interface for imaging observations.
Use the following interface for all grism observations.
- As of 4 December 2007, in conjunction with the Cycle 17 Call for Proposals, the NICMOS ETCs have been updated and revised to reflect a number of corrections and improvements relative to those used in previous years. We recommend that observers use these most up-to-date ETCs for their NICMOS calculations.
- On November 8, 2004, an updated NICMOS ETC was delivered. This delivery included a second new user interface for NICMOS grism spectroscopy. Other updates to the ETC include calculation of sky background given target RA and DEC coordinates and the ability to upload user spectrum files directly to the ETC server from inside the browser interface (instead of FTP-ing the file to the public STScI anonymous FTP server). Here, we describe the previous enhancements to the ETC delivered November 25, 2003.
- In the period between July 2004 and 28 April 2005, the ETC contained an error that led the ETC to overestimate the detector quantum efficiency. We recommend that any calculations performed in the affected period be repeated in order to obtain the correct exposure time or signal-to-noise estimates. Details are here.
To access your previous ETC requests, visit the Previous Requests Page.
For coronagraphic observers, please refer to this advisory note.
For problems or questions, please email firstname.lastname@example.org.
The old ETC is still available. It has more limited functionality and it has not been updated. Known problems and limitations are described here. It will be retired soon.