LUCY
Lunar Uptime & Communication Yardstick
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Landing window assessment

Surface

154 km working zone
Shaded relief of the lunar south pole from LOLA terrain
SELECTED SITE
↑ 0° E
×1.0
LOLA shaded relief, display lighting · Dimmed: outside the 154 km zone · Labels approximate

Mission setup

Observer location

Supported zone: within 154 km of the pole, approximately 84.9–90° S. Click the map to pick a site.

Mission interval / UTC
h UTC
d

Mission profile
m
h
h
%

Example setup, not a recommendation.

Assessment

Assessment

NOT CALCULATED
Settings changed. Run again to update.
Not calculated yet

Pick a site on the map or enter coordinates, then press Run assessment.

Visibility timeline

SunEarthBlocked
Exact visibility intervals / UTC

Daily geometry

10 min steps
Solid: body altitude · Dashed: terrain horizon

Sun

Earth

UTC—
Visibility—

Current geometry

QuantitySunEarth

Window report

QuantityValueUnit

Method, data & sources

What LUCY calculates

For a site and a mission window, LUCY checks minute by minute whether the Sun is visible (power) and whether the Earth is visible (direct communication), then compares the longest night, the Sun share and the longest communication gap with the mission's thresholds. The calculation is deterministic and reproducible, with no AI. It shows landing windows that meet the thresholds; it does not guarantee mission success.

How visibility is decided

Terrain horizon: for every site, the highest terrain elevation angle in 720 directions (0.5° each) out to 150 km, computed from the LOLA elevation model on the lunar sphere. A body is visible when its altitude is above the terrain horizon in its own direction. Sun and Earth positions come from the JPL DE440 ephemeris in the lunar body-fixed frame (MOON_ME), computed locally with Skyfield.

Data

Supported domain

Within 154 km of the lunar south pole, approximately 84.9–90° S. Dates 2000–2050. Windows 1–60 days. A site outside coverage returns "insufficient terrain data", not a failed assessment.

Limits of the model

Body centres (no partial Sun disc), no eclipses, direct line of sight to Earth. Window intervals are resolved to a minute; daily charts use 10-minute samples. Search map shares use hourly samples of start times; top search results are recalculated at 1-minute resolution. The map background is shaded LOLA relief with a fixed display light, not the illumination of any date. Crater labels are approximate.