The Search for Habitable Worlds. 1. The Viability of a Starshade Mission

Abstract

ABSTRACT. As part of NASA's mission to explore habitable planets orbiting nearby stars, this article explores the detection and characterization capabilities of a 4 m space telescope plus 50 m starshade located at the Earth-Sun L2 point, known as the New Worlds Observer (NWO). Our calculations include the true spectral types and distribution of stars on the sky, an iterative target selection protocol designed to maximize efficiency based on prior detections, and realistic mission constraints. We conduct simulated observing runs for a wide range in exozodiacal background levels (ε ¼ 1-100 times the local zodi brightness) and overall prevalence of Earth-like terrestrial planets (η ⊕ ¼ 0:1-1). We find that even without any return visits, the NWO baseline architecture (IWA ¼ 65 mas, limiting FPB ¼ 4 × 10 À11 ) can achieve a 95% probability of detecting and spectrally characterizing at least one habitable Earth-like planet and an expectation value of ∼3 planets found, within the mission lifetime and ΔV budgets, even in the worst-case scenario (η ⊕ ¼ 0:1 and ε ¼ 100 zodis for every target). This achievement requires about 1 yr of integration time spread over the 5 yr mission, leaving the remainder of the telescope time for UV-NIR general astrophysics. Cost and technical feasibility considerations point to a "sweet spot" in starshade design near a 50 m starshade effective diameter, with 12 or 16 petals, at a distance of 70,000-100,000 km from the telescope.

Enabling the direct detection of earth-sized exoplanets with the LBTI HOSTS project: a progress report

“…Two sample types have been determined based on three different methods. For FGK stars, which are of greatest interest for exoplanet direct imaging missions, two differing selection methods were compared, one we call the Mission Oriented Selection is determined by applying a target selection code derived from work on the New Worlds Observer (Turnbull et al [33]), and the other is a Mission Independent Selection derived from the Unbiased Nearby Survey (UNS) sample (Phillips et al [34]). Both selection methods were applied to stars with spectral types later than F5 and resulted in a sample of 49 nearby sun-like stars, which we call the "Sun-like Sample".…”

WFIRST-AFTA coronagraph science yield modeling with EXOSIMS

“…4 Information to be stored or accessed by this module will include target positions and proper motions at the reference epoch (see Sec. 2.1.6), catalog identifiers (for later cross-referencing), bolometric luminosities, stellar masses, and magnitudes in standard observing bands.…”

“…The star catalog is based on a curated database originally developed by Turnbull et al, 4 with updates to stellar data, where available, taken from current values from the SIMBAD astronomical database. 12 Target selection is performed with a detection integration time cutoff of 30 days and a minimum completeness cutoff of 2.75%.…”

The LBTI hunt for observable signatures of terrestrial systems (HOSTS) survey: a key NASA science program on the road to exoplanet imaging missions

“…Two sample types have been determined based on three different methods. For FGK stars, which are of greatest interest for exoplanet direct imaging missions, two differing selection methods were compared, one we call the Mission Oriented Selection is determined by applying a target selection code derived from work on the New Worlds Observer (Turnbull et al [25]), and the other is a Mission Independent Selection derived from the Unbiased Nearby Survey (UNS) sample (Phillips et al [26]). Both selection methods were applied to stars with spectral types later than F5 and resulted in a sample of 49 nearby sun-like stars, which we call the "Sun-like Sample".…”