← INDEX — FIG. 00 — URANUS 97.77°, NEPTUNE 28.32°
19.2 AU · 30.2 AU
TILT
URANUS & NEPTUNE, THE ICE GIANTS
Two planets about four times the width of Earth.
BEGIN — CHAPTER 01 →CH.01 / 08 — A PLANET ON ITS SIDE
Forty-two years of daylight at the pole
Uranus: 97.77°.
Poles get more light than the equator.
DAILY-MEAN SUNLIGHT AT LATITUDE φ
Q = (S/π)(H₀ sinφ sinδ + cosφ cosδ sinH₀) · cosH₀ = −tanφ tanδ · sinδ = sinε sinλ
Circular-orbit model.
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Model notes.
CH.02 / 08 — SUNLIGHT AND SIGNAL FALL AS 1/r²
Too dim for solar panels, too far for a quick reply
1/369 and 1/902 of Earth's sunlight.
29,900 and 21,600 bit/s achieved.
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Assumptions.
CH.03 / 08 — VOYAGER 2 AT URANUS, 24 JANUARY 1986
Six hours that wrote the textbook
81,500 km, 10 moons, 2 rings.
An unusual day; Webb's 29th moon.
Scale notes.
CH.04 / 08 — VOYAGER 2 AT NEPTUNE, 25 AUGUST 1989
The closest pass of the whole Grand Tour
4,800 km; Great Dark Spot gone by 1994.
Triton: retrograde, −235 °C, 8 km plumes.
TWO VISITS, ONE SPACECRAFT
Uranus: 8.4 years after launch, 81,500 km · Neptune: 12.0 years, about 4,800 km
Computed from dates.
CH.05 / 08 — THE LONG WAY OUT
Sixteen years the cheap way
Hohmann: 16 years, C3 ≈ 127.
No Jupiter 2033–2044.
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Two-body model.
CH.06 / 08 — THE URANUS ORBITER AND PROBE
Top priority, not yet a project
Decadal: highest priority.
Status, October 2026.
THE 2026 CONCEPT, IN NUMBERS [13]
2 Next Gen RTGs · 350 W at end of mission · ~34-day orbits · 4-year moon tour · 19.5 kbit/s Ka-band · probe entry ≤ 50 g
Concept details.
Status as of 9 October 2026.
CH.07 / 08 — LEGACY
One flyby each, forty years of questions
A few hours of one spacecraft.
CH.08 / 08 — REFERENCES