26 May 1967, when the telemeter failed. The initial spin rate was 33 rpm, and the spin axis direction was right ascension 272.8° and declination 21.5°. The spin rate decreased with time to 2 rpm on 9 September 1965. For the balance of its life, the spacecraft was coning or tumbling at a rate of about 1 rpm. Re-entry Some sources erroneously record Explorer 26 as having decayed from orbit in 1978, a conclusion reached by early decay rate projections. Based on continued satellite tracking data, Explorer 26 was confirmed to have decayed from orbit on 23 August 2021 after over 56 years in orbit. NASA's S-3C scientific satellite, the Energetic Particles Explorer-D, named Explorer 26 after launch was launched on 21 December 1964 into an elliptical 310 x 26200 km x 20.1° orbit and operated for 2.4 years. SATCAT number 00963, it reentered on 23 August 2021 after 56.7 years in space. See also Explorer program Explorer 15 References Explorers Program Spacecraft launched in 1964 Spacecraft which reentered in 2021