A trillion pairs a second leave Earth. How many reach Mars?
Every stage of the link multiplies the rate by a factor from a tested model: optics, the atmosphere, the spreading of the beam over hundreds of millions of kilometres, pointing jitter, detectors, memories, and the Sun getting in the way. Sunlight reflected by Earth competes with the signal at the Mars receiver, and every herald it causes stores noise. Then the pair must wait in a memory for Earth's two classical bits. The stream below is drawn from qll/systems/mars_budget.py, ported line by line to docs/js/budget_core.js and checked against it.
the stream · band height is the logarithm of the pair rate after each stage; red stages are where it dies
when · Earth–Mars range over two synodic periods, shaded where the Sun blocks the line of sight
architecture
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hardware
source and operations
background light
what the Mars receiver sees · Earth's phase, the transmitter, and the receiver's one mode
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what arrives
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the key bank · one synodic period of secret key, and the bank that lets the messenger spend it evenly
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the same link with each demonstrated memory
| memory | coherence | retrieval | pairs / day | fidelity after storage | verdict |
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A memory is paid for twice here: its retrieval efficiency at both ends multiplies the rate, and its coherence time sets the fidelity after the wait. Assumptions (all adjustable in MarsLinkDesign): 1550 nm, transmit optics 0.8, receive optics 0.7, detectors 0.9, Earth elevation 40° and the Sun 12° below the horizon for a ground station, weather and operations duty 0.5, storage for one round trip, depolarizing memories, Earth's near-infrared albedo 0.3, airglow 10⁻⁷ W m⁻² sr⁻¹ nm⁻¹.