Neighboring Planet Outposts: Location and Opportunity

The value of multipoint observations in understanding

the 3D, large scale impacts of solar activity on the space

environment has been well-demonstrated using both

serendipitous combinations of separated heliospheric

spacecraft measurements, as well as the planned pairings

represented by Helios and STEREO. But appropriately

instrumented planetary missions have also provided unique

vantage points for space weather studies, especially

in the inner heliosphere. Venus and Mars prove

especially useful because of their positions bracketing

1 AU where STEREO and L1 in-situ observations are

made. The relative frequency of radial and

Parker Spiral alignments result in extra

opportunities to observe evolution and extent of solar wind structures

and solar energetic particle events, and their planetary interaction

impacts. At present, MAVEN and Mars Express regularly produce

a combination of solar wind plasma, magnetic field and SEP

information -while Venus has only historical information

from PVO and Venus Express available for studies,

New mission opportunities at these planets should

be of interest to heliophysics researchers, especially

in light of the need for context for interpreting upcoming

PSP perihelion and Solar Orbiter out-of-ecliptic

observations. Promoting basic space environment

measurements at Mars and Venus on a regular basis

is well worth the effort from both planetary science and

heliophysics perspectives.