National Aeronautics and

Space Administration

2023 Moon to Mars Architecture Concept Review 1white paper 2023 Moon to Mars Architecture

Overview

The communications disruption and delay 

profile for a Mars mission will depend on the 

trajectory profile of the mission, though some 

generalizations can be made. While several 

factors can contribute to communications 

disruption and delay, this paper addresses the 

unique physical characteristics of Mars transit 

and Mars-vicinity operations. 

Assuming nominal operation of communications 

systems, disruption occurs when the Sun or 

other planetary objects are directly between 

Earth and a spacecraft, rover, or other element. 

This obstruction severs the line of sight as 

the signal travels between Earth and Mars 

and results in a communications blackout. 

Interference from solar radiation can also 

degrade that signal without full obstruction. 

The duration of a blackout depends on the 

communications protocol and signal strength. 

For any crewed, roundtrip mission to Mars, 

direct spacecraft-to-Earth communications 

blackouts are inevitable and can last weeks. 

Depending on the mission profile, these 

blackout periods can occur while the crew is in 

transit or the vicinity of Mars. NASA analyses 

show that blackout periods generally occur 

while the crew is at Mars for long-stay missions, 

and during transit for higher energy, short-stay 

missions.

For communications delays, the time required 

for signal to travel from Earth to a Mars element 

and back is a function of the distance separating 

the two. Communications signals travel at the 

speed of light in a vacuum, so signal transit time 

is the element’s distance from Earth divided by 

the speed of light. 

The exact profile of the delay will depend on 

trajectory, but the one-way communications 

delay for a crewed Mars mission can be upward 

of 21–23 minutes, with the longest delays 

occurring while the crew is at Mars or just after 

Mars departure. 

Communications disruptions and delays for 

crewed Mars missions necessitate significant 

crew and system autonomy from Earth-based 

mission control, which drives certain system and 

operational requirements. Communications 

relay assets could potentially provide some 

relief from communications blackouts but 

would not eliminate delays, as the signal must 

still travel the same distance or farther to reach 

its destination.

Background

Approximately every 26 months, Earth and 

Mars are on exact opposite sides of the Sun. 

Astronomers call this celestial phenomenon — 

where all three celestial bodies are in a straight 

line — “conjunction.” Figure 1 illustrates this 

feature that results from the relative orbits of 

planets. 

Conjunction presents a challenge to any Mars 

mission in that it results in a communications 

disruption. This is because communications 

signals cannot pass through the Sun directly. 

The Sun also distorts any signals that pass too 

close due to the interference of solar energy. 

For robotic missions, operations during these 

conjunctions are typically managed to reduce 

impacts on science objectives and increase 

spacecraft safety. Operating robotic platforms 

in safe mode and standing down of any 

operational activities reduces risk during a 

conjunction. However, those options are not 

available to a crewed mission, as crew activities 

must continue even in the absence of direct 

communications with mission control.

The extent of any communications disruption 

or blackout depends on communications 

equipment and sensitivity to interference from 

solar energy. A graphical representation of that 

angle, θ, can be seen in Figure 1. Communications 

equipment highly sensitive to solar interference 

would experience communications disruption 

with a higher value of θ.

Mars Communications 

Disruption and Delay
2023 Moon to Mars Architecture Concept Review 2

Figure 1. This diagram illustrates Earth-Sun-Mars conjunctions creating line-of-sight disruption between 

Earth and Mars (left) and the angle definition for communications disruption analysis (right).

Mars or 

Spacecraft

For the initial assessment of the blackout period during 

Mars missions, NASA assumed a θ value of 2° based on 

the current understanding of communications protocols 

and their susceptibility to signal disruptions. However, 

higher bandwidth communications protocols may have 

higher sensitivity to disruptions and could have a higher 

θ value.

Example 850-Day Short-Stay

Roundtrip Mission to Mars

Figure 2 shows the communications disruption and delays 

for a representative, 850-day, short-stay mission to Mars. 

The top chart shows the Sun-Earth-spacecraft angle, and 

the bottom chart shows the one-way communications 

delay profile for this representative trajectory. 

A 2° θ angle results in a communications disruption 

of three weeks of blackout around 450 days into the 

mission, about 100 days after the crew departs Mars 

from their surface mission. This three-week period 

of communications disruption and blackout would 

require significant crew and system autonomy from 

mission control. This drives certain system capabilities, 

redundancies, and operational needs for mission design 

and/or the addition of communications relays. 

Example 1000-Day Long Mars 

Stay–Class Roundtrip Mission

Figure 3 shows the communications disruption and 

delays for a representative, 1,000-day mission typically 

associated with a minimum-energy roundtrip mission to 

Mars. Assuming an Earth-Sun-spacecraft angle threshold 

of 2°, the trajectory results in a communications blackout 

period of approximately 13 days during the phase of the 

mission in the vicinity of Mars. 

Depending on the surface concept of operations, the crew 

could be on the surface of Mars performing exploration 

duties. This blackout period occurs about 100 days into 

the 300-day stay in the vicinity of Mars. This means 

critical events related to planetary arrival and departure 

should not be impacted by the disruption. For delays in 

communications, the blackout period coincides with the 

longest delay period of just over 20 minutes one-way, 100 

days after Mars arrival.

Summary

Communications blackouts and delays are unavoidable 

for crewed missions to Mars, though blackouts could 

be mitigated with communications relay elements. The 

design of crewed Mars missions must reflect this shift in 

communications paradigm when compared to low-Earthorbit or lunar missions. 

System and crew autonomy should be a significant 

focus in Mars mission design. NASA analyses can 

provide representative mission profiles, with estimated 

communications delays and blackout periods to inform 

those design parameters.

References

McBrayer, K., Chai, P., Judd, E., Communication Delays, 

Disruptions, and Blackouts for Crewed Mars Missions, 

AIAA ASCEND, 2022
2023 Moon to Mars Architecture Concept Review 3

Figure 2. Communications disruption and delay for 

an 850-day, short-stay, roundtrip Mission to Mars 

with a communications blackout of about 21 days 

and maximum one-way communications delay of 22 

minutes. Both blackouts occur during the inbound 

leg of interplanetary transit.

Figure 3. Communications disruption and delay 

profile of a representative minimum energy, 

approximately 1,000-day stay, roundtrip mission 

to Mars with a communications blackout of about 

13 days and a maximum one-way communications 

delay of 21 minutes. Both occur while the crew is in 

Mars orbit or on the surface of Mars. 

Outbound

Inbound

Outbound

Inbound

Deep Space Duration: 985 days

Mars Vicinity Duration: ~300 days

Solar Distance: ~1.0AU to ~1.6AU

Deep Space Duration: 850 days

Mars Vicinity Duration: 51 days

Solar Distance: ~1.0AU to ~1.8AU