SADs are typically observed using soft X-ray and Extreme Ultraviolet (EUV) telescopes that cover a wavelength range of roughly 10 to 1500 Angstroms (Å) and are sensitive to the high-temperature (100,000 to 10,000,000 K) coronal plasma through which the downflows move. These emissions are blocked by Earth's atmosphere, so observations are made using space observatories. The first detection was made by the Soft X-ray Telescope (SXT) onboard Yohkoh (1991–2001). Observations soon followed from the Transition Region and Coronal Explorer (TRACE, 1998–2010), an EUV imaging satellite, and the spectroscopic SUMER instrument on board the Solar and Heliospheric Observatory (SOHO, 1995–2016). More recently, studies on SADs have used data from the X-Ray Telescope (XRT) onboard Hinode (2006—present) and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO, 2010—present). In addition to EUV and X-ray instruments, SADs may also be seen by white light coronagraphs such as the Large Angle and Spectrometric Coronagraph (LASCO) onboard SOHO, though these observations are less common.