A guide to Hinode and EIS terminology#

Angstrom - This is the unit of wavelength used by EIS and 10 Angstroms = 1 nm. If someone refers to the “Fe XII 195 line” it is understood that 195 is given in Angstroms.

Chief Observer (CO) - Each of the three instruments assigns a Chief Observer (CO) who is responsible for preparing the observation plan for that instrument. The CO changes each week and is provided by the US, Japan, UK and Norway teams. The EIS CO role is often performed remotely.

Chief Planner (CP) - The Chief Planner is responsible for creating the satellite pointing file in coordination with the three COs. The CP also oversees the compilation and upload of the instruments’ observing plans. The CP is always based at ISAS and often takes the role of one of the COs at the same time.

Compression - The onboard software has several options for compressing EIS data in order to reduce the data volume transferred to Earth. DPCM is a lossless compression mode, and the others are all JPEG (lossy) modes. For example, JPEG98, JPEG98, JPEG50. The lower the number, the more compressed the data. Because JPEG works on 8x8 blocks of pixels, all EIS wavelength windows must have sizes that are multiples of 8.

Raster - The basic observation unit of EIS. It is either a single scan of the EIS slit over a spatial area, or repeated exposures at a fixed slit position (“sit-and-stare” mode).

Slit - The image formed by the EIS telescope passes through a slit, and then is dispersed by the grating to yield a spectrum on the detector. There are four slit options with widths corresponding to 1, 2, 40 and 266 arcsec on the Sun.

Slot - alternative name for either of the two wide slits of EIS, i.e., the 40 and 266 arcsec slits.

Study - This is the observation unit that makes up the EIS timeline. It comprises one or more rasters. Each study has a unique acronym (a 20 character string) and an ID number.

Window - An EIS detector image has wavelength in the X-direction and spatial information in the Y-direction. A “window” is a rectangular sub-region of this image. For example, if you want to observe the Fe XII 195.12 emission line then you would design a raster that retrieves a window on the detector that is centered on this line. Most EIS observations have up to 25 windows that pick out specific spectral features. An exception is the “full-CCD” observation that takes the entire wavelength range of the detector image. In this case there are four windows: there are two detectors that are read out in halves. The full CCD can not be retrieved for every observation due to telemetry constraints. Note that the full Y-range of the detector corresponds to 1024 arcsec, but the onboard software limits the downloaded image to at most 512 arcsec.