Toward a Continuous Record of the Sky

It is currently feasible to start a continuous digital record of the entire sky sensitive to any visual magnitude brighter than 15 each night. Such a record could be created with a modest array of small telescopes, collectively generating no more than a few gigabytes of data daily. Alternatively, a few small telescopes could continually repoint to scan and record the entire sky down to any visual magnitude brighter than 15 with a recurrence epoch of at most a few weeks, again always generating less than 1 Gbyte of data each night. These estimates derive from CCD ability and budgets typical of university research projects. As a prototype, we have developed and are utilizing an inexpensive single-telescope system that obtains optical data from about 1500 deg2. We discuss the general case of creating and storing data from both an epochal survey, in which a small number of telescopes continually scan the sky, and a continuous survey, composed of a constellation of telescopes each dedicated to continually inspect a designated section of the sky. We compute speciÐc limitations of canonical surveys in visible light, and estimate that all-sky continuous visual light surveys could be sensitive to magnitude 20 in a single night by about 2010. Possible scientiÐc returns of continuous and epochal sky surveys include continued monitoring of most known variable stars, estab- lishing case histories for variables of future interest, uncovering new forms of stellar variability, discovering the brightest cases of microlensing, discovering new novae and supernovae, discovering new counterparts to gamma-ray bursts, monitoring known solar system objects, discovering new solar system objects, and discovering objects that might strike the Earth.