Solar Orbiter Executive Report
29 Jun 2005The Science Payloads and Advanced Concepts Office has undertaken a detailed assessment of the Solar Orbiter mission. Its recently published findings are summarised here.
The Solar Orbiter mission will provide the next major step forward in the exploration of the Sun and the heliosphere to solve many of the fundamental problems remaining in solar and heliospheric science. It incorporates both a near-Sun and a high-latitude phase.
The near-Sun phase of the mission enables the Orbiter spacecraft to approach the Sun as close as 48 solar radii (~0.22 AU) during part of its orbit, thereby permitting observations from a quasi-helio-synchronous vantage point. At these distances, the angular speed of a spacecraft near its perihelion approximately matches the rotation rate of the Sun, enabling instruments to track a given point on the Sun surface for several days.
During the out-of-ecliptic phase of the mission (extended mission), the Orbiter will reach higher solar latitudes (up to 35º in the extended phase), making possible detailed studies of the Sun’s polar caps by the remote-sensing instruments.
The Sun's atmosphere and the heliosphere represent uniquely accessible domains of space, where fundamental physical processes common to solar, astrophysical and laboratory plasmas can be studied under conditions impossible to reproduce on Earth or to study from astronomical distances. The Solar Orbiter mission, through a novel orbital design and an advanced suite of scientific instruments, will aim to help scientists achieve major breakthroughs in the understanding of solar and heliospheric physics by:
As a result, the following scientific goals for the mission have been identified:
The main missions requirements are outlined below:
The Solar Orbiter mission design is based on a cruise phase and a science phase. The cruise phase comprises the Earth escape and a trajectory that remains close to the ecliptic in order to bring the Orbiter into a Venus resonant orbit. The mission design for the science phase, which begins with a Venus Gravity Assist Manoeuvre (GAM) reducing the perihelion distance. Later Venus GAMs increase the orbital inclination to more than 30 degree with respect to the solar equator.
Two possible mission scenarios are under consideration. The originally preferred scenario uses Solar Electric Propulsion and the alternative approach uses traditional chemical propulsion in Deep Space Manoeuvers in the cruise phase.
Based on initial analysis of these two mission scenarios the following conclusions have been reached:
The assessment study of the Solar Orbiter has addressed all mission areas, from the scientific requirements to the payload complement, the space and ground segments, including all corresponding programmatic aspects.
Specific attention has been given to the reference payload, in the form of a dedicated industrial study as well as of internal activities, in order to prepare adequately for the future payload AO and maintain a certain degree of control over the corresponding spacecraft resources. These activities have indicated that, given the number and complexity of the instruments on board, such an attention should also be given in the following mission phases. The system level study has indicated that two mission profiles are viable:
b) Back-up profile, using chemical propulsion, with a 3.3 year cruise phase (with lower development risk).
In both cases, all critical design drivers have been analysed and, while design challenges do exist, no major feasibility questions have been raised, showing a feasible mission, compatible with the nominal launch date of October 2013.