Case 1: HabEx 4H hybrid, metric C1

The HabEx 4-meter H, or hybrid, case consists of a coronagraph used in a blind search for the detection of exoplanets and a starshade for the spectral characterization of exoplanets. The hybrid case utilizes the strength of the coronagraph, which is its agility to observe and revisit numerous targets, and the strength of the starshade, which is to provide a continuous spectrum over more than 100\% bandpass. Observation scheduling is of critical importance to the starshade design reference mission. Observation scheduling, using the realistic solar constraints and slew transits between targets, shows that the design reference mission is achievable and verifies that the design of the starshade (dry mass, fuel mass, and propulsion) closes.

The coronagraph blind search is the limiting factor for the HabEx 4H hybrid architecture. To be promoted for characterization, the star must have three exo-earth detections spanning more than half a period. The promotion rate parameter in the dynamic detection plot shows that the promotion rate is higher for higher completeness stars. In comparison to time of first observation (also in the dynamic detection plot) the stars whose initial observation occurred late in the mission did not result in target promotions insufficient mission time remained for the requisite orbit determination epochs.

The dynamic plot for characterization shows the mean unique exo-earth characterizations (at least one characterization), the mean characterization integration time of the synthetic planets around that particular star, and the mission elapsed time of the first characterization. Repeat characterizations, such as those in the HabEx baseline concept of operations, do not contribute to the yield metric; the yield metric captures the contribution from at least one spectral characterization. The fraction of earths characterized to earths present shows the likelihood that an earth will be characterized if an exo-earth exists around a particular star. For nearby, high completeness stars, the likelihood of characterizing an earth if it is exists is close to 1.

The mission elapsed time of first observation shows a strong correlation to completeness. This is reasonable considering that the high completeness stars will be observed first in the coronagraph blind search, having a higher probability of detection, will complete orbit determination and thus target promotion, and by extension, characterization, earliest.

Dynamic Detection and Characterization Plots

These plots show several quantities relating to detection and characterization in distance/luminosity coordinates. Each star in the target list is represented by one dot in the plot, shaded according to the selected quantity. Some stars in the target list are not observable by the instrument due to SNR limitations, and they are shown in gray.

Hovering over the dot drills down to the target name with exact numerical values and uncertainties. All quantities shown by shading are averages across the runs in the ensemble, and the indicated standard deviation is the standard deviation across the ensemble. This standard deviation captures the inherent variability of the quantity due to the random simulated universe and observational scheduling, if applicable. For instance, the number of exo-earths per star is approximately 0.24, and thus the variance of the underlying Poisson count of exo-earths is also 0.24, for a typical standard deviation of 0.49. The popup also shows the standard error of the given average, which is the above standard deviation divided by the square root of the ensemble size. This “standard error of the mean” is the error in the given average due to Monte Carlo sampling.

Interactive Detection Plot Widget

Detection QOI for Plot Shading:

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Interactive Characterization Plot Widget

Characterization QOI for Plot Shading:

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PNG static plot list

Histogram of earths characterized

A histogram showing the average, across the ensemble, of the number of exo-earths successfully characterized. The bars sum to one.

Final frame

A map-format plot, in heliocentric longitude and latitude coordinates, of a single representative mission observation history. Target stars are shown as colored dots, and the Sun is marked with S. The solar system keepout on the final day of the mission is illustrated: gray for kept-out areas, and white for observable. The sequence of characterizations is shown as a line with arrows indicating slew direction. Only one type of observation is shown per target. Gray target stars were not observed, detections are shown as solid-color dots (without a black circumference), and characterizations are shown as dots with a black edge. The two dot sizes separate cases of four or more observations vs. less than four. Successful observations of habitable-zone planets are shown as green, those for other planets are purple, and unsuccessful observations are red. Thus, a small purple dot with a black edge indicates one to three successful characterizations of a non-habitable-zone planet. more

A map-format plot, in heliocentric longitude and latitude coordinates, of a single representative mission observation history. Target stars are shown as colored dots, and the Sun is marked with S. The solar system keepout on the final day of the mission is illustrated: gray for kept-out areas, and white for observable. The sequence of characterizations is shown as a line with arrows indicating slew direction. Only one type of observation is shown per target. Gray target stars were not observed, detections are shown as solid-color dots (without a black circumference), and characterizations are shown as dots with a black edge. The two dot sizes separate cases of four or more observations vs. less than four. Successful observations of habitable-zone planets are shown as green, those for other planets are purple, and unsuccessful observations are red. Thus, a small purple dot with a black edge indicates one to three successful characterizations of a non-habitable-zone planet. less

Observation timeline

A time-based plot showing the observing timeline – detections, taking of spectra, slews, and other non-exoplanet observations – from a single representative mission. Slews are shown in narrow gray bars along with taking of spectra. In all timelines, alternating dark and light colors are a visual aid to separate events which are sometimes closely spaced. Integration windows shorter than one day have been enlarged to one day to ensure they are visible in the plot. more

A time-based plot showing the observing timeline – detections, taking of spectra, slews, and other non-exoplanet observations – from a single representative mission. Slews are shown in narrow gray bars along with taking of spectra. In all timelines, alternating dark and light colors are a visual aid to separate events which are sometimes closely spaced. Integration windows shorter than one day have been enlarged to one day to ensure they are visible in the plot. less

Keepout for chars

(will write caption if included). Timeline: Keepout Overlaid with Observations Showing Characterization Targets and Keepout Detections: Blue; Characterizations: Green; Obscured: Gray Mission Observation and Keepout Timeline for 229154300: Year 1

Event count, dets and chars

Histogram of the average number of events related to observations: detections, characterizations, and detections resulting in target promotion. The values for each sum to one when added across the event count on the abscissa.

Cumulative mission obs

Time spent in different modes (detection, characterization, slew), cumulatively as a function of mission elapsed time. Detection time can overlap slew time. Standard deviation across the ensemble is illustrated by the plot bars.

Cumulative Earth chars

The average number of exo-earths characterized versus time, as a cumulative total up to the given time. One value is plotted for each month of mission elapsed time. The error bars are at plus and minus one standard deviation, again computed across the ensemble. The line for all characterizations is the sum of unique characterizations and revisits.

Cumulative det earths

The average number of exo-earths detected versus time, as a cumulative total up to the given time. One value is plotted for each month of mission elapsed time. The error bars are at plus and minus one standard deviation, again computed across the ensemble. The line for all detections is the sum of unique detections and revisits.

Mean slew time histogram (60 days)

Histogram of the mean time used for slews across each simulation in the ensemble. The bins of slew time are two days wide, and the histogram values sum to one. The error bars are the standard deviation of the relative frequency in that histogram bin, computed across the ensemble.

Cumulative fuel use

The average cumulative fuel use versus mission time. Fuel devoted to slew and to stationkeeping, as well as their sum (the total fuel use), are shown. One point per month is plotted, together with an error bar which is the standard deviation of fuel usage to that time across the ensemble

Sky coverage of longest exposure window (HabEx 4H only)

A map-format plot, in heliocentric longitude and latitude coordinates, showing the maximum observing interval obtainable at that target star across the five-year mission, in days. Targets near the ecliptic plane have a smaller observing interval which limits integration time.