SCHED was written by R.C. Walker (RCW) in the late 1970’s for Mark II VLBI scheduling. It was part of the Caltech VLBI package. It received a number of modifications over the following decade by the author and others, including Tim Pearson, John Benson, and Mark Hodges. Beginning in 1988, the program was extensively revised by RCW to accommodate VLBA, and eventually global VLBI, scheduling. In 1991, a project to write VLBA OBSERVE was been begun by the NRAO with the programming being done by Wes Young. SCHED development was at a a minimal level during this development project as it was thought that the program would soon be retired.
In the Fall of 1995, the VLBA OBSERVE project was cancelled. An intensive effort was made then to add many of the features whose need had become apparent during the period of minimal development. In the Spring of 1996, Huib van Langevelde of JIVE, then stationed at NRAO, began work on the VEX additions which became a significant part of the program. Also, at about that time, Brian Butler provided the code needed to add the planet capability that is important for single dish pointing and gain measurements at high frequencies. Rick Lively provided systems support including writing makefiles and helping with interactions with users who were trying to install the programs on other machines. In January 1998, Franco Tinarelli of Bologna delivered the first code for point-and-click control of the SCHED plotting functions and has been supporting the plot functions ever since. In 2002, Cormac Reynolds took over support of the Vex portions of the code from Huib.
SCHED is currently the primary scheduling program used for astronomical VLBI. It is also capable of scheduling many types of observations on the VLA.