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Observing with EIS with the new antenna#

Table of Contents#

About this page#

This Wiki page deals with typical observing constraints that you need to bear in mind when making a proposal for observing with Hinode EIS.

Practical constraints?#

Time#

OP Periods#

An OP Period[1] is the period of time during which an observing programme (plan) is defined. e.g. from 10:23 UT on 2008/05/02 to 11:19 UT on 2008/05/04. (The start and end of each OP period are determined by the pattern of ground-station contacts, which varies from day to day.)

Since the transition to stable operations under the S-band antenna, typical OP Period durations have been two or three days.

Once solar activity begins to increase, and solar unpredictability increases accordingly, Hinode may consider more frequent (i.e., one-day-long) OP Periods.

Eclipse Season#

During eclipse season[5], the line of sight between the spacecraft and the Sun grazes the Earth's atmosphere, causing attenuation (and ultimately complete absorption) of the light that would otherwise be seen by each of the instruments. This attenuation affects first the EUV and X-ray bands, then later the visible wavelength range.

The duration of night-time is calculated for the visible band, and in the peak of eclipse season (around mid-July [3]) this duration is about 20 minutes. EUV absorption begins about 10 minutes before the calculated entry into optical night (NGT_ENTRY) and ends about 10 minutes after exit (NGT_EXIT). Thus, the EIS operations team recommend that you leave a ten-minute buffer around s/c night in eclipse season.

South Atlantic Anomaly (SAA)#

On most orbits, Hinode passes over the South Atlantic Anomaly (SAA), where high-energy particles penetrate lower into the magnetosphere. During such passes, significantly more cosmic rays are observed on the EIS detector images. These passes are calculated at the same time as other orbital events (such as Eclipse Season NGT events, when appropriate), and times vary each day. Such passes normally last approximately 10 to 20 minutes.

However, around 12 UT, Hinode experiences a so-called Golden Period where the SAA itself does not intercept the s/c orbit. Because the SAA passes vary in time, the start of this period can range (approximately) from 10 to 11 UT, with the end being anywhere from 14 to 16 UT.

The EIS team use a rule of thumb that a 5-minute window around SAA events is sufficient to account for the variability in size of the SAA.

N.B. the old vulnerability to changing slit/slot choice during an SAA pass is no longer relevant, following an on-board software update in August 2007

Volume#

Since moving to Hinode's S-band antenna for downlinks, the spacecraft typically can downlink something like 200 Mb[2] per 24 hours. This

Do you have examples of what kind of observations are best suited for EIS?#

Yes :-)

Go over to the Study4LowDataVolume page on this Wiki for examples of programmes recently developed for EIS.

Why can my old HOP no longer be run?#

How is the HOP process different?#

Nomenclature#

OP

[1]Operation Programme

S-band antenna

[4] Hinode's secondary antenna, with a bandwidth of 262 kb/s.

Eclipse Season

[5] The portion of the year where the sun is occluded by the Earth's atmosphere for a fraction of each orbit. It lasts from late April until early September.

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Other Notes

[2]: Remember, Mb stands for megabits (1024 × 1024 bits), as distinct from MB (for megabytes). 1 MB = 8Mb.

[3]: Is this correct? I know it's approximately true, since we start in late April, and come out of eclipse season in early September.