COR1

COR1 is the inner coronagraph instrument of the SECCHI suite aboard NASA’s Solar TErrestrial RElations Observatory (STEREO). Launched in 2006, STEREO consists of two nearly identical spacecraft, STEREO-A and STEREO-B, which provide stereoscopic views of the Sun and the surrounding heliosphere. Each spacecraft carries a COR1 telescope designed to image the solar corona in visible light, enabling study of the near-Sun environment and the early evolution of coronal mass ejections (CMEs).

The COR1 instrument uses an external occulter to block direct solar glare, revealing the faint solar corona in a narrow field of view. Its typical field of view covers roughly 1.4 to 4 solar radii from the Sun, placing it in the region where CMEs accelerate and interact with the surrounding corona. COR1 produces white-light images that capture coronal structures such as streamers and CME initiation features, providing key data for understanding solar eruptive events.

As part of SECCHI, COR1 data complement those from the outer coronagraph COR2 and the heliospheric imagers HI1 and HI2, enabling continuous tracking of CMEs from near the solar surface out into the inner solar system. The instrument has contributed to space weather research by helping to characterize CME onset, speed, direction, and early evolution, information used to forecast potential geomagnetic disturbances at Earth and in the heliosphere.

Data from COR1 are archived and made available to the scientific community through the STEREO data portals, where researchers can access calibrated imagery and supporting metadata. COR1 remains a foundational component of the multi-instrument approach that characterizes the STEREO mission’s solar and heliospheric observations.