TPF-I SWG Report - Exoplanet Exploration Program - NASA
TPF-I SWG Report - Exoplanet Exploration Program - NASA
TPF-I SWG Report - Exoplanet Exploration Program - NASA
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C HAPTER 4<br />
Channel SNR<br />
10.0<br />
Channel SNR<br />
1.38 / rotn<br />
# rotations<br />
53<br />
Planet signal rms<br />
Random noise<br />
Systematic noise<br />
0.091 /s 0.042 /s 0.051 /s<br />
Local Zodi leak Stellar size leak Null floor leak<br />
photon noise photon noise photon noise<br />
0.027 /s 0.033 /s 0.006 /s<br />
Planet signal rms Local Zodi leak Stellar size leak<br />
Null floor leak<br />
Null stability<br />
0.091 /s<br />
2.3E-08<br />
71 /s<br />
1.8E-05<br />
106 /s<br />
2.6E-05<br />
3 /s<br />
7.5E-07<br />
at planet harmonics<br />
1.3E-08<br />
Amp-phase error<br />
ΔA Δφ / rad<br />
0.13% 0.0011<br />
Dynamic<br />
Control systems<br />
Fringe track<br />
Metrology<br />
Tip/tilt<br />
Shear<br />
Disturbances<br />
Beamtrain<br />
Static<br />
Coatings<br />
Reflectivity<br />
Alignment<br />
Beam combiner<br />
π phase sh<br />
Figure 4-5. Simplified <strong>TPF</strong>-I error budget for the signal-to-noise ratio (SNR) required for ozone<br />
detection at 10-μm wavelength.<br />
4.2 Performance Models<br />
The two key performance models are described in this section: the Interferometer Performance<br />
Model (IPM) for predicting the SNR on a specified target; and the Star Count Model for<br />
estimating the number of targets that can be surveyed over the duration of the mission.<br />
4.2.1 Interferometer Performance Model<br />
The <strong>TPF</strong> Interferometer Performance Model (IPM) is maintained as a series of Excel spreadsheets and is<br />
used both to estimate the performance of different architectures, and to derive the requirements for the<br />
baseline design. The spreadsheet performance model is run as a bottom-up calculation; that is, the overall<br />
performance is calculated based on the specified low-level inputs (as opposed to a top-down suballocation<br />
approach). The inputs can be adjusted and balanced until the desired output performance is obtained, at<br />
which point the input values assumed become the requirements on the instrument.<br />
64