Subject: SRP test
From: "John C. Ries" <[email-masked]>
To: [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked], [email-masked]
Date: Thu, 23 Mar 2006 16:59:42 -0600

Hi Everyone,

Bruce suggested a test where I look at the impact of the SRP model on 
the SLR/DORIS dynamic orbits. So I re-ran the first 90 cycles with a 
3% change to the full SRP (box-wing) effect. It does indeed lead to a 
120-day (117 days to be exact) variation in the centering, mainly in 
Z. There was an effect on X and Y, but it was only 0.5 mm. The effect 
on Z was about 2 mm (see plot, where I multiplied the z-shift by -30 
and compared it to the beta-prime angle...you can see the 
correlation). The effect on the inertial centering, as measured by 
the crossover means, was negligible.

So I presume a larger scaling of the SRP could lead to a larger Z variation.

I've tested the effect of drifts in the Z component of the reference 
frame and found that the orbits tended to follow the Z-drift, at 
least about 90% of it. But it looks like there is some wiggle room in 
that remaining 10%, and one can get some modulation on top of that 
due to SRP.

JR