UMBRAS Performance

UMBRAS Performance

The design has associated performance characteristics. Below are some graphs of these.

Range of SPIDER vs Number of targets/year.

Target observation Rate of N-class UMBRAS occulter

The graph above shows the maximum operating range, r (in kilometers), of the SPIDER UMBRAS craft for a given number of targets per year (N).

Max Range vs S/C Mass and Observation Rate

SEP Max range as function of S/C mass & obs rate
Approximate maximum average range of SPIDER from the telescope as a function of SPIDER Mass and Targets/year assuming N-class design. This relation exists because of the acceleration limits inherent to solar electric propulsion. Curve families can shift depending upon such parameters as dry weight of S/C, science time on target, and length of mission.

The graph above shows curves representing the maximum operating range (in kilometers) for a SPIDER of given total (starting wet) mass, Msc (varying the propellant carried), acheiving a given number of targets per year(N).

Range of SPIDER as function of Number of Targets/year and Number of Transit engines.

Fewer engines=closer+same observation rate, or =same range+lower observation rate

The graph above shows a family of curves representing the maximum operating range (in kilometers) achievable for a given number of targets per year (N) for a specified number of continuously operating transit engines (j). Not shown is the impact on mission lifetime.

Exoplanet Light Loss for different NGST-class SPIDER ranges.

Aperture blockage effects in Spot-mode.

The graph above gives curves showing the amount of light lost (in astronomical magnitudes) due to geometric occlusion of an 8-meter aperture for given range of SPIDER, r (kilometers), and separations, theta (arcseconds) between a faint source and the edge of the screen for the idealized case of the aperture centered behind a square occulter.

How quickly SPIDER moves.

Max turnover velocity and distance travelled

A sense of scale. Two curves are shown: the colored curve is the maximum velocity achieved near turnover in meters/second of SPIDER during a given time under acceleration, and the black curve shows the distance (kilometers) it will have travelled assuming acceleration until turnover and then decceleration. The vertical dashed lines show time durations of 1-hour, 1-day, and 1-week.

How big SPIDER appears from NGST (far field).

Angular size of given screen at given distance.

The curves on the graph above show the apparent size of a screen (in arcseconds) for given ranges between NGST and SPIDER, y (in kilometers), and for given screen sizes, s (in meters).

How big SPIDER appears from NGST (near field).

Angular size (in arcseconds) of given size screen at given distance.

The same as shown above, except the vertical scale shows closer separations between NGST & SPIDER.

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