By Peter Lawson
The coronagraph experiments have been doing extremely well this year. Preliminary results of experiments in laser light have now shown that Olivier Guyon’s PIAA (Phase Induced Amplitude Apodization) and Gene Serabyn’s Vector Vortex coronagraphs each operate with average contrasts of about 6 x 10-10. That is good news indeed. While each individual is taking care of the requisite paperwork for their milestones, they are also forging ahead with broadband experiments that will eventually enable the detection and characterization of planets. The best contrasts demonstrated to date are still those by John Trauger’s Hybrid Band-Limited Lyot mask, with contrasts of 5 x 10-10 with a 10% bandwidth – already at a level to detect Jupiter-like planets around nearby stars.
Now that the Science and Technology Definition Teams (STDTs) have been selected for the probe-scale mission studies, and a coronagraph for the 2.4-meter telescope will continue to be studied, the Program’s technology will be reevaluated and prioritized to determine the best path forward. With the probe-scale missions, the high-level challenge is certainly to define a compelling science mission with a life-cycle cost of less than $1B, this being the notional budget cap for a probe. With the 2.4-meter telescope, the challenge is to be ready for flight with coronagraph technology that will work well with that telescope’s secondary mirror and its six supporting struts. There is plenty of good work to be done.
With the help of all our coronagraph and occulter stakeholders, I’ve been taking a new look at the experimental data to better understand the relative performance of the different designs and to more faithfully capture their strengths. This analysis will examine how well each design enables the detection of planets and has more dimensions than a simple analysis of contrast versus angular separation. It will be a busy summer.