Sent_en: 2fil Mkn 421 was observed three times with Chandra's Low-Energy Transmission Grating (LETG), twice in conjunction with the High Resolution Camera (May 2000 and July 2003) and once with the Advanced CCD Imaging Spectrometer (October 2002).
Sent_yy: Inobserbahan ang Mkn 421 nang tatlong beses sa Low-Energy Transmission Grating (LETG) ng Chandra, dalawang beses sa kasabay ng High Resolution Camera (Mayo 2000 at Hulyo 2003) at isang beses sa Advanced CCD Imaging Spectrometer (Oktubre 2002).