Sun-outage (sun-blinding) events Brief disturbances in GEO space communications occur twice yearly when which bodies are aligned?

Introduction / Context:
Sun-outage, also called sun-blinding, is a predictable interference period when the Sun passes directly behind a GEO satellite as seen from an Earth station. The Sun’s broadband RF noise overwhelms the downlink, momentarily degrading service.

Given Data / Assumptions:

• GEO satellite, fixed azimuth/elevation at the Earth station.
• Solar apparent motion causes alignment near equinoxes.
• Event lasts minutes per day over several days, twice a year.

Concept / Approach:
When the Sun, the satellite, and the Earth station lie on the same line, the Earth station antenna main lobe views the Sun behind the satellite, injecting intense solar noise into the receiver front end and reducing carrier-to-noise.

Step-by-Step Solution:
Define alignment: Earth station → satellite → Sun along boresight.Result: maximum received solar noise temperature in the main beam.Effect: temporary loss or degradation of signal (a few minutes), repeating daily during the event window.

Verification / Alternative check:
Operators publish sun-outage prediction tables per site longitude/latitude, satellite slot, and dish size, confirming alignment geometry.

Why Other Options Are Wrong:

• Any two-body alignment alone does not guarantee the antenna boresight sees the Sun through the satellite direction.
• Sun and Moon alignment is unrelated to this RF noise event.

Common Pitfalls:

• Confusing sun-outage with rain fade; the former is predictable and seasonal, the latter is weather-dependent.
• Assuming outages affect the uplink; the downlink is the typical limiting leg.

Final Answer:
Sun, satellite, and Earth station (all three in line)