The intermediate Palomar Transient Factory
The intermediate Palomar Transient Factory (iPTF) is a fully-automated, wide-field survey for a systematic exploration of the optical transient sky. This project is built upon the legacy of the Caltech-led Palomar Transient Factory (PTF), which saw first light in March 2009. With improved software for data reduction and source classification, the project has achieved significant successes in the early discovery and rapid follow-up studies of transient sources.
This project uses a large field camera subtending 7.8 square degrees on the sky. Formerly the CFHT 12k mosaic camera, the unit was signficantly reworked for PTF, which included replacement of the liquid cryogen dewar with a cryo-cooler, as well as a new field corrector, filter exchanger and shutter mechanism. The camera has 11 active 2048x4096 CCDs. The telescope is the venerable 1.2-meter (48 inch) Samuel Oschin Telescope at Palomar Observatory, the same telescope used for the original photographic Palomar All-Sky Survey.
The nominal survey is at R-band, but additional observations are also made at g-band The standard exposure time per frame is 60 seconds, yielding a 5-sigma limiting magnitude of 20.5 and 21 for R- and g-band respectively. The iPTF has carried out various experiments with different cadences, from a 5-day cadence to 90 seconds. The project encourages well designed interesting experiments for new discoveries. The data are processed at the Infrared Processing and Analysis Center, which also maintains the primary data archive. Realtime transient processing also takes place at LBL. All of the extragalactic transient sources and galactic variable stars discovered by iPTF are archived separately by a Transient Marshal and Galactic Marshal.
The iPTF project is a scientific collaboration between Caltech; Los Alamos National Laboratory; the University of Wisconsin, Milwaukee; the Oskar Klein Centre in Sweden; the Weizmann Institute of Science in Israel; the TANGO Program of the University System of Taiwan; and the Kavli Institute for the Physics and Mathematics of the Universe in Japan.
In 2017 iPTF will transition to the Zwicky Transient Factory (ZTF). Using a reworked version of the same telescope as iPTF, ZTF will use a new camera, with an instantaneous field-of-view of 47 square degrees. This new camera will enable a full scan of the visible sky every night, and will be a direct lead-in to the LSST era.