National Geographic Explorer is an American documentary television series that originally premiered on Nickelodeon on April 7, 1985, after having been produced as a less costly and intensive alternative to PBS's National Geographic Specials by Pittsburgh station WQED. The first episode was produced by WQED and featured long-time Explorer camerman Mark Knobil, who is the few staff members with the franchise during all 24 seasons. The program is the longest-running documentary television series on cable television. Presented every Sunday from 5:00 PM to 8:00 PM, the original series was three hours in length, containing five to ten short films. Although the National Geographic Society had been producing specials for television for 20 years prior to Explorer, the premiere of the series required an increase in production from 4 hours of programming a year to 156 hours. Tim Cowling and Tim Kelly were the executive producers for the series during this transition.In its 24 years on television, Explorer has worked for five television outlets. In February 1986, Explorer moved to TBS, where it had a successful run until September 1999, when it moved to CNBC. In October 2001, the series moved to MSNBC. In June 2003, the series re-launched itself on MSNBC as Ultimate Explorer, with Lisa Ling as the host. On July 8, 2004, Explorer joined the National Geographic Channel, where currently it airs every Tuesday night at 10:00 PM.