1968

Caltech/Jet Propulsion Laboratory 65-cm telescope proposal for Skylab II

1972

65-cm prototype installed at Big Bear Solar Observatory

1973

MSVC/Itek 150-cm telescope study for shuttle

1973

Goddard Space Flight Center (GSFC) 100-cm telescope study for Spacelab

1974

Announcement of Opportunity for "Scientific Definition of Space Shuttle Missions for Solar Physics Spacelab Payloads"

1975

Initial work of One-Meter Solar Telescope Facility Definition Team

1976

Spacelab Optical Telescope proposed by Association of Universities for Research in Astronomy, Inc., to NASA

1978

Spacelab Optical Telescope top ranked of four candidate solar facilities

1979

Solar Optical Telescope project started at GSFC

1980

Facility definition teams terminated

1982

Selection of science teams, telescope and instrument contractors

1983

Phase B studies completed

1983

Phase C/D deferred due to Spacelab budget reductions and difficulties with Hubble Space Telescope

1984

Formal NASA approval for FY 86 new start but FY 86 budget capped at FY 85 study level by Congress

1985

Phase C/D funds deleted from FY 87 budget request by Office of Management and Budget (OMB)

1986

High Resolution Solar Observatory (HRSO) project started at GSFC; studied as Space Station payload

1986

Phase C/D funds deleted from FY 88 budget request by OMB

1987

HRSO redesigned as a free flier

1988

Restructuring of HRSO to restore capabilities lost in 1986

1989

New science objectives formulated to accommodate changes in hardware

1990

GSFC New Business Committee pledges center to OSL budget and manpower plan

1990

Request for proposals issued for Phase B contractors

1990

Favorable nonadvocacy review; favorable review by Space Science and Applications Advisory Committee (SSAAC)

1990

OSL listed as the highest-priority mission for initiation as early as 1992 in the Office of Space Science and Applications Strategic Plan

1991

SSAAC recommends 1998 as earliest start date for OSL