July 2006 SHARP ip Calculations

The instrumental polarization was calculated from the centered Jupiter ip data taken in July. Data processing was as follows:

1. Gather 4-file sets of Jupiter ip
2. In Matlab, run Huabai's ip program, 'pijupiter(total # of files)'
3. Run 'qu4(total # of files)' to get qu data
4. Create list of file elevations
5. Using the values of q and u from qu4, and the list of elevations, run Megan's program 'ip_fit_par' (uses 'ipchisq.m'). Write down fit parameters amp, phase, qoff, uoff
6. Run 'plot_m3(amp, phase, HWP, qoff, uoff)', with HWP defined in Giles' 4/12 memo.

The instrumental polarization is composed of both a fixed component and a component that varies due to movement of M3. Raw q and u values can be fit with the following sin/cos curves:

q = amp*cos(2*(-el - phase)) + qoff

u = amp*sin(2*(-el - phase)) + uoff

The four parameters, amp, phase, qoff, and uoff, are found by minimizing the chisquared function with qraw, uraw, and elevation for each file as input.

For July 2006, we find the following parameter values:

• amp = 0.0029
• phase = 0.24 (in degrees)
• qoff = 0.0041
• uoff = 0.0012

These values correspond to an M3 amplitude of 0.29% polarization, and a static contribution of 0.43% polarization with angle phi_inst_corr = 176.8.

The raw q and u data with their corresponding curve fits are given below:

raw u vs elevation

A plot of the variable M3 polarization angle vs elevation can be found here. As you can see, phi_inst_corr varies from 5 degrees to 95 degrees as elevation changes from 0 to 90 degrees.