The official insignia for the Approach and Landing Test Program flown by the Space Shuttle Enterprise during 1977.
This circular, red, white and blue emblem has been chosen as the official insignia for the Space Shuttle Approach and Landing Test (ALT) flights. A picture of the Orbiter 101 "Enterprise" is superimposed over a red triangle, which in turn is superimposed over a large inner circle of dark blue. The surnames of the members of the two ALT crews are in white in the field of blue. The four crew men are astronauts Fred W. Haise Jr., commander of the first crew; Joe H. Engle, commander of the second crew; and Richard H. Truly, pilot of the second crew. ALT is a series of flights with a modified Boeing 747 Shuttle Carrier Aircraft (SCA) as a ferry aircraft and airborne launch platform for the 67,300 kilogram (75-ton) "Enterprise". The Shuttle Orbiter atmospheric testing is in preparation for the first Earth-orbital flights scheduled in 1979.
https://images.nasa.gov/details/S76-30340
Original:  NASA Vector:  affius