The Interstellar Heliopause Probe (IHP) Technology Reference Study (TRS) investigates the feasibility of a mission to the heliopause region. The main focus is on heliospheric physics in the outer heliosphere and local interstellar medium. This requires that the IHP travel a distance of 200 AU from the Sun. This challenging mission profile will require a set of enabling technologies that are not only of benefit for this type of mission, but also for missions to the outer planets.
The Interstellar Heliopause Probe
The main scientific objective of the IHP is to investigate the interface region between the local interstellar medium and the heliosphere and to truly reach the interstellar medium at 200 AU. The scientific questions that the IHP will aim to answer as it travels towards this region are:
The IHP mission profile requires the spacecraft to travel a distance of 200 AU from the Sun within 25 years. To reach the interstellar medium in the shortest possible time the spacecraft will have to be launched in the direction of the heliosphere nose, which is located at 7.5° latitude and 254.5° longitude, in the ecliptic coordinate frame.
With solar sails the IHP can meet these requirements by means of a solar sail with a characteristic acceleration of 1.0 mms-2. To obtain the required solar system escape velocity the IHP will perform two close flybys of the Sun (at minimum 0.25 AU). Closer distances would provide even higher escape velocities, however with the current materials selected for the sail design 0.25 AU distance will be the closest possible distance to keep the sail at the required temperatures.
The preliminary concept for IHP employs a spinning solar sail. The characteristics of the sail can be seen in the table below.
The current mass budget for IHP is given in the table below.
The IHP Technology Reference Study is intended to identify the technologies required for a mission to the interstellar Heliopause and beyond. The main technologies requiring development are outlined below:
Solar Sail Material: The sail material will have to withstand a solar flux of approximately 16 times the flux at Earth. During its required 5 year lifetime it is important that the sail keep its optical properties, as the performance of the sail is directly dependent on the reflectivity of the coating.
Lightweight Booms: The current study baseline is utilizing lightweight booms to provide rigidity to the structure. These booms have a specific mass in excess of 100 g/m and are longer than 120 m. Further development of lighter booms would greatly benefit the IHP.
Solar Sail Phase Attitude Determination and Control: There are several options for performing attitude control. The options currently under consideration include a gimbaled boom between the sail and spacecraft, moving masses along the boom structure, and tip vanes or thrusters on the booms.
Solar Sail Jettison Mechanism: A low mass jettison mechanism is required that can safely jettison the sail from the spacecraft after 5 years of sailing with a minimum risk of collision between the extended sail structure and the spacecraft.
Communication: The communication system for IHP will be limited to an average downlink data rate of around 200 bps at 200 AU. Currently RF and optical communication are being considered. For the optical communication issues like the acquisition strategy, lightweight components and laser lifetime must be solved. For an RF system development of lightweight antennas and highly efficient travelling wave tube amplifiers are required.
Lifetime and Autonomy: The design lifetime of the IHP must be more than 25 years. The consequences to all subsystems, components and materials must be evaluated in detail and specific test procedures must be developed.
This study was completed in 2006. It was performed by SRE-PAP with the assistance of the Kayser-Thede, Surrey Space Center, University of Glasgow and Cosine Research.
For further information about this study please contact the study manager:
Dr. Peter Falkner