Time Period of Proposed Observation:
Start and End Dates: No specific time period, whenever a suitable coronal hole appears and there is sufficient time to collect the data.
Number of Days: Sufficient time to collect the data, about 24 hours.
Continuity: Interruptions should be short enough that no major structural changes occur in the coronal hole.
Time Window in Day:
Minimum Duration: 24 hours. The archival observation had 2 hour total exposure time with the 2h slit. Assuming the 1h slit collects half as many photons and that the EIS sensitivity has remained constant over time, a 24 hour exposure time would reduce the counting statistical noise by a factor of 2.4.
Interruptions: Should not be a problem, as long as interruptions are short enough that the major coronal hole structures do not vary too greatly. This probably means collecting the 24+ hours of observations within a few day period.
Target of Interest:
Polar coronal hole from just below the limb to large heights. In Solar-Y, roughly 885h to 1395hand at Solar-X = 0h. Ideally, a large well-formed polar coronal hole that is centered over the pole so that there is minimal contribution from foreground and background quiet Sun regions.
Target of Opportunity: Yes.
Hinode Instruments and Observeables:
EIS - 1h slit with a fixed pointing at about Solar-X = 0h and vertically extending from about
+/- 885h to +/- 1395h (From slightly below the limb to large heights above it).
Cadence is not important, as the intent is to integrate all the data in the end. In the archival data one often finds repeated observations with 10 minute cadences, and something like this would be suitable.
Wavelengths - many wavelengths are desireable in order to perform a DEM and separate coronal hole from quiet Sun contributions. A full CCD observation would be excellent. In case of telemetry limitations, the following is a prioritized list of lines, some of these can be picked up in a single window, even though we list the lines separately. Wavelengths are in Angstroms.
High Priority: Fe X 184.54, Fe VIII 185.21, Fe VIII 186.60, Fe XII 186.88, Fe XI 188.22, Fe XI 1883.0, Fe IX 188.50, Fe IX 189.94, Fe XII 195.12, Fe IX 197.86, Fe XIII 202.04, Fe XIII 203.79 & 203.82, Si VI 246.00, Mg VI 270.39, Fe XIV 270.52, Si X 271.99, Si VII 275.36, Si VII 275.68, Fe XV 284.16
Medium Priority: O VI 183.94, O VI 184.12, Fe XI 189.71, Fe X 190.04, Fe XII 192.39, Fe XII 193.51, Fe X 193.72, Fe VIII 194.66, Fe XII 196.64, Si VI 249.12, He II 256.32, Fe X 257.26, Si X 258.37, Si X 261.06, Mg VI 268.99, Si VII 272.65, Mg V 276.58, Si X 277.26, O IV 279.63, O IV 279.93
Lower Priority: Fe X 174.53, Fe XI 180.40, S X 264.23, Mg VII 276.15
Data Volume Estimate - ~8 Mb per exposure. This is based on the EIS data we used before, such as eis_l0_20090423_151714, for which the FITS file is 25 Mb for a full-CCD readout containing 3 exposures.