IN this thesis I describe the development and validation of a generic time domain simulator of exoplanet transit spectroscopy called ExoSim, and apply it to various problems in the field. ExoSim models both the astrophysical scene and the optical system in an end-to-end simulation, outputting a time series of images akin to a real observation. The simulator was validated through a series of tests against predictions, alternate simulations and published data, showing it was accurate to within 5% of most comparisons. ExoSim modeled the Hubble Wide Field Camera 3 IR instrument, finding that scanning mode was superior to staring mode (38% less noise), with no significant excess noise. The results supported uncertainties in published studies for GJ 1214b. ExoSim was used in the ARIEL Phase A study, playing a key role in formulating and verifying an instrument design that was low risk and compatible with the science case of spectroscopically surveying 1000 exoplanets. Spectral jitter noise was found to be a feature of ARIEL observations, but using ExoSim it was shown this could be mitigated in data reduction without design level changes. ExoSim was used to quantify the uncertainties due to stellar variability on the transmission spectrum, finding that noise from pulsations and granulation is not significant in ARIEL observations. For spots, variations of +3.9 to -5.2% in contrast ratio were projected for GJ 1214b and +0.9 to -0.5% for HD209458b in the visual range, but in the mid-IR range variations fall well within the photon noise limit. ExoSim was used to simulate observations of the TRAPPIST-1 system, from which we found that ARIEL could characterise primordial H2-He atmospheres on all 7 planets, but that only planets b and h would be candidates for observing high molecular weight atmospheres. Overall, ExoSim was found to be a valuable tool applicable to diverse problems in the field of transit spectroscopy.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:732296 |
| Date | January 2017 |
| Creators | Sarkar, Subhajit |
| Publisher | Cardiff University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://orca.cf.ac.uk/108680/ |
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