NASA Astrobiology Institute (NAI)

In this project we are comparing an existing model of the Earth with images and spectra of the Earth obtained from a distance spacecraft. The VPL Earth model uses Earth observing satellite data including atmospheric conditions and cloud cover to simulate both images and spectra of the Earth on a given day of observation. The comparision between the model and data will help us improve our model, and will also provide information on how detectable some of the Earth’s environmental characteristics would be to an observer in another planetary system.

The existing VPL Earth model, a 3-D spectroscopic model of the Earth, developed by the original Virtual Planetary Laboratory team (Tinetti et al., 2006) has been ported to the University of Washington. We have also worked to document and modify the code to allow more rapid configuration of new model “days” (dates of observation for the Earth) and to enhance its atmospheric and surface spatial resolution. Work is currently underway to optimize it for use on a parallel-computing cluster and as a readily-accessible community tool.

This model is being validated via analysis of data from the joint EPOXI NASA Discovery Mission of Opportunity (PIs Drake Deming: EPOCh and Mike A’Hearn: DIXI). This mission reuses the Deep Impact spacecraft to observe extrasolar transiting planets, a comet, and to observe the Earth as an extrasolar planet from distances in excess of 0.2 AU. The VPL Earth model will be validated against the latter dataset, for which we have obtained 3 separate 24 hr observing periods on March 19, May 25 and June 5, 2008. We are currently using the revised VPL Earth model to perform forward modeling to generate synthetic lightcurves and spectra for the Earth on March 19, 2008 for comparison with the data. This work was presented by doctoral student Ty Robinson at AbGradCon 2008.