O3 MR calculation for UV-photometer

v2022.02.03a uses three intensity measurements per calculated mixing ratio, but only two measurements of pressure and temperature.

have

T1 ... T2       ... x
p1 ... p2       ... x
I1 ... I2(zero) ... I3
----------------------
t1 ... t2       ... t3
----------------------
 |___________________|
        |
   ... MR(t2)   ...

want

T1 ... T2       ... T3
p1 ... p2       ... p3
I1 ... I2(zero) ... I3
----------------------
t1 ... t2       ... t3
----------------------
 |___________________|
        |
   ... MR(t2)   ...