DELTA 1 R/B

DELTA 1 R/B is a spent rocket body associated with United States, launched on 1972-07-23 from Vandenberg Space Force Base, United States on the ERTS A launch. After more than 54 years in orbit, it is one of the longest-surviving objects in the space catalogue. It orbits in Low Earth Orbit (LEO) at altitudes between 547 km and 664 km with an inclination of 98.5°. It travels at approximately 27,212 km/h (7.56 km/s), completing one full orbit every 97 minutes — that’s roughly 14.88 orbits per day. Its near-polar, sun-synchronous orbit means it passes over any given point on Earth at approximately the same local solar time, ideal for consistent Earth observation lighting conditions. At its current altitude, the estimated orbital lifetime before atmospheric re-entry is ~10–25 years. Spent rocket bodies like DELTA 1 R/B are among the largest pieces of uncontrolled space debris and are priority targets for collision avoidance manoeuvres and future active debris removal efforts.

DELTA 1 R/B orbits at an average altitude of 606 km in a sun-synchronous orbit (SSO), a specialised subset of LEO where the orbital plane precesses to maintain a constant angle relative to the Sun. This provides consistent lighting conditions on every pass — essential for Earth observation, weather monitoring and environmental science. Within ±50 km of DELTA 1 R/B’s average altitude, there are currently 1,639 active payloads and 734 tracked debris or rocket body fragments — notable neighbours include ONEWEB-0050, STARLINK-3005, STARLINK-3090. This makes it one of the more crowded altitude bands, containing roughly 8.8% of all active satellites. With an inclination of 98.5°, DELTA 1 R/B passes over latitudes between 98.5°N and 98.5°S, providing near-global coverage including the polar regions. Polar and near-polar orbits are used for reconnaissance, weather monitoring and Earth-observation missions that need to image every part of the planet. United States operates approximately 13,206 active satellites in total, of which 1,050 share a similar altitude band with DELTA 1 R/B.