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Table 1 Objectives and requirements for visibility calculations

From: Visibility analysis of Phobos to support a science and exploration platform





Remote sensing of the Mars atmosphere and surface

Visibility of Mars > 0 min

Visibility of Mars dayside and nightside

No map required due to Phobos’ tidal lock and equatorial orbit. All Mars local times are covered equally. Dayside and nightside are both observed ~ 3 h 50 min per orbit

Visibility from Deimos during Mars occultation

If stations are located on both Phobos and Deimos, attenuation of a signal transmitted between the two captures information about Mars’ atmosphere and ionosphere

Map of Phobos quantifying the number of occultation events showing locations where the line of sight to Deimos intersects Mars’ surface

Radio/ranging science: Geodesy, dynamics, gravity, fundamental physics

Visibility from Deimos: ≥ 2 h per day

Both cases are mostly covered by the GPS requirement

Boolean map of Phobos true where visibility from Deimos is ≥ 2 h per day

Visibility (laser ranging) from Earth ≥ 2 h per day

Boolean map of Phobos true where visibility from Earth is ≥ 2 h per day

Phobos in-situ science

No requirements

All locations on Phobos have science potential


Mars space environment monitoring

Visibility from Sun (solar wind) 2 h per day

Solar wind monitoring

Boolean map of Phobos true where solar visibility ≥ 2 h per day

Data relay

Visibility from Earth ≥ 6 h per day, except during solar superior conjunction

6 h is considered a basic requirement (including consideration of eclipses) for ESA planetary missions

Boolean map of Phobos true where Earth to Phobos visibility ≥ 6 h/day

Visibility from Mars > 0 min

Minimum elevation angle (above horizon) = 10°

Link to surface rover for data downlink or telecommanding. As an example, we use the NASA Mars Science Laboratory landing site at Gale crater: 5.4°S, 137.8°E

Boolean map of Phobos true where a rover landing site to Phobos visibility > 0 min/day (accounting for a buffer in elevation of + 10° above horizon)

Visibility from Jupiter: at least 3 h per day, during solar superior conjunction (Earth-Jupiter)

3 h per day is estimated to provide sufficient data volume for downlink of housekeeping data and uplink of telecommands from and to the JUICE spacecraft

Boolean map of Phobos true where Jupiter to Phobos visibility ≥ 3 h, there is a solar superior conjunction

Global Mars positioning system

Visibility from Deimos ≥ 2 h per day

For positioning, laser ranging, radio tracking

Boolean map of Phobos true where Deimos to Phobos visibility ≥ 2 h per day

Visibility to Phobos from Mars and Deimos simultaneously

Concurrent visibility of Phobos and Deimos from the surface of Mars allows better positioning

Map of Mars showing hours per day where Phobos and Deimos are concurrently visible

Power (assuming solar power system)

Solar illumination should be ≥ 4.5 h per day

This time duration is estimated based on previous studies (ESA Concurrent Design Facility Study Report: Phobos Sample Return 2014)

Boolean map of Phobos true where visibility from Sun is ≥ 4.5 h per day

Public outreach

Visibility from Mars: once per day on the dayside of Mars

Public outreach ‘Phobos-webcam’

Visualisation to demonstrate outreach potential