From "Don Mickey"
<mickey@ifa.hawaii.edu>
Subject Transit plan
Date Fri, October 27, 2006 5:02 pm
I suggest we use the standard Na "movie" scheme, but disable the
polarization modulation.
I believe this is DLM16. I have copied all the templates from DLM16
into a new SID called JMP01. If you pull up JMP01 it should look
exactly like DLM16, but you can modify things without messing up our
standard obs.
You will need to run dark and flat, but not calseq nor calrtd unless
the software requires you to.
In the mag template, there are four settings for each retarder, plus
two zeros at the end. Change the four so that all are the
same as the fourth one; I think this is around 1100 for both retA and
retB. Roughly like:
retA: 1100 1100 1100 1100 0 0
retB: 1200 1200 1200 1200 0 0
The wavelength steps will be unchanged.
You will need to set the FP Z, X and Y to get the line centered and the
plates parallel. Maybe the best thing is to run the FPflat routine
using the 6302 line for a whole day, from 1800 to 2400 or as close as
you can get. Run it every half hour or so so that you get a reasonable
number of points, plot a smooth curve through them and use that as your
settings. Then you don't have to mess with FPflat during the transit.
...
-----
From "Kevin Reardon"
<kreardon@arcetri.astro.it>
Subject Re: Fwd: Re: sodium atmosphere of Mercury
Date Thu, October 26, 2006 5:42 pm
I think it is good that the IVM can also be used to look for the sodium
atmosphere during the transit. Note that the FWHM of the sodium
absorption profile from Mercury is probably only around 60 mA,
approximately equivalent to the instrumental profile of the IVM. The
previously observed equivalent widths peaked at only 15 mA. The
absorption should be in the red wing of the sodium line, approximately
100 mA from the line core. It might be good to concentrate primarily
on on this wavelength range (with some scans of the full line).
I'm not sure the advantages of the Stokes measurement, but it might
be useful to obtain more than one image at a time for each
wavelength position (and polarimeter setting). This will allow the
variations in the underlying solar structure to be better accounted for
when looking for the intensity decrease due to Mercury's
atmosphere.
-----
On Wed, 25 Oct 2006, Glenn Schneider wrote:
I spoke with Don a short while ago - he called me here at Steward - to
discuss the observation set-up and details as he had summarized by
email. He thought it best to not wait until Monday.
Basically, I think we agreed on most of what he had written. One
modification is that we should collect polarization (Stokes)
data. I am actually not sure how useful (if at all) that would be
- though remembering, of course, Mercury has a magnetic field, it would
be interesting if w could detect it and its magnetosphere - but maybe
that would be the needle in the haystack against the Sun.
Mercury's dipole moment is about 5e12 T m^3 (or about 4E-4 tat of
Earth). It seems to me we really have no significant penalty for
using the modulator to obtain the Stokes images, and of course should
also be able to recover total intensity data post-facto.
Also, when Don says we can run pretty continuously thought the transit,
we WILL have to pause to repaint on Mercury (apparently tracking
on Mercury is not an option). We can do that "manually" with a
guide camera, but I will send Don an ephemeris in the event we can set
that up ahead of time - that may result in less dead time.
-----
From "Don Mickey" <mickey@ifa.hawaii.edu>
Subject Re: contact information
Date Thu, October 26, 2006 4:28 pm
We can only measure down to about 0.1%, and in this case we're looking
at an extremely high-contrast
edge so image motion from frame to frame will reduce the polarization
sensitivity a lot. Not the right
instrument, I think.
On Oct 26, 2006, at 1:16 PM, Glenn Schneider wrote:
> Don: Just out of curiosity... What sort of P% precision, and
> detection floo,r can you achieve with IVM. The crazy question
> is, might it be possible to detect the effects of the Mercurian
> magnetosphere against the solar "background". My "gut"
> says in the noise... but my gut has been wrong (on rare occasion)
;-)
----
>
> ----- Forwarded message from Don Mickey
<mickey@IfA.Hawaii.Edu> -----
> Date: Tue, 24 Oct 2006 16:23:30 -1000
> From: Don Mickey
<mickey@IfA.Hawaii.Edu>
> Reply-To: Don Mickey <mickey@IfA.Hawaii.Edu>
> Subject: Re: sodium atmosphere of Mercury
> To:
Jay.M.Pasachoff@williams.edu
>
> Jay,
>
> I suggest that you use the IVM in its standard operating mode,
> that we use for getting Na magnetograms. The instrument
> scans the D1 line with 24 mA steps, about 1A total range.
> Spectral resolution is something like 60 mA, I think.
> We measure polarization at each step, requiring 4 frames
> with different modulator settings. Image cadence is about 1 second;
> one line scan thus takes about 160 seconds.
>
> It would be possible to modify the sequence, for example
> make all the modulator settings the same so no polarization
> information is obtained. Then you would get four frames
> at each wavelength. Or change the size of the wavelength
> step or the number of steps across the line (max 40).
>
> The Fabry-Perot is set up in a collimated configuration,
> so its passband center varies with field angle. That means
> just taking on-band and off-band pairs isn't satisfactory
> (you don't have the same wavelength all over the field),
> so you have to do some sort of wavelength scan.
>
> This is in the "data" camera of the IVM. The "geometry" camera
> also sees the Fabry-Perot comb spectrum, but with a blocking
> filter that transmits about 30 FP orders rather than just the
single
> order at the D1 line. So you would get "continuum" and "line"
> images simultaneously.
>
> This program could be run pretty much continuously during the
> transit.
>
> I will NOT be in Hawaii for the transit. I know I told you this
before,
> but it means that you will need to decide if this instrument
> is suitable for what you want to do, and what the parameters
> of the observation ought to be, in the next day or two so
> I can work with Garry to customize the setup.
>
> It might be useful to have a phone conference. Jeff and I will both
> be here in Honolulu next Monday and we could set up a
> call time, probably the morning Hawaii time. I will be gone
> after Monday 10/30.
>
> --Don
Kopp, G., Lawrence, G., and Rottman, G., T
he Total Irradiance Monitor
(TIM): Science Results, Solar Physics, 230, 1, Aug. 2005, pp.
129-140
which includes both the transits of Venus and Mercury (2003). {Greg
Kopp <greg.kopp@lasp.colorado.edu>}