The interstellar dust detection conditions with the DESTINY+ Dust Analyzer

The DESTINY+ spacecraft will be launched to the active asteroid (3200) Phaethon in 2025. The spacecraft will be equipped with the DESTINY+ Dust Analyzer (DDA) which will be a dust telescope hosting a time-of-flight impact ionization mass spectrometer. In addition to the composition of impacting dust particles, the instrument will measure the particle mass, velocity vector, and surface charge.

Here, we study the detection conditions of DDA for interstellar dust during the DESTINY+ mission. We use the interstellar dust module of the Interplanetary Meteoroid environment for EXploration model (IMEX; Sterken et al., 2013; Strub et al., 2019) to simulate the flow of interstellar dust through the Solar System. Extending earlier work by Krüger et al. (2019) we here consider the entire DESTINY+ mission, i.e. the Earth-orbiting phase of the spacecraft during the initial approximately 1.5 years after launch, the nominal interplanetary mission phase up to the Phaethon flyby, and a four-years mission extension beyond the Phaethon flyby. The latter may include additional asteroid flybys.

To predict dust fluxes and fluences we take into account a constraint for DDA to not point closer than 90 degrees towards the Sun direction for health and safety reasons of the instrument and in order to avoid electrical noise generated by solar photoelectrons.

For the Earth orbiting phase after launch of DESTINY+ our simulations predict that up to 28 interstellar particles will be detectable with DDA in 2026. In the following years the interplanetary magnetic field changes to a focussing configuration for small (<0.1 μ m) interstellar dust particles. This increases the total number of detectable particles to 50 during the interplanetary mission of DESTINY+ in 2027. In 2028 and 2029/30 approximately 160 and 190 particles will be detectable, respectively, followed by about 500 in 2030/31.

We also make predictions for the detectability of organic compounds contained in the interstellar particles which is a strong function of the particle impact speed onto the detector. While organic compounds will be measurable only in a negligible number of particles during the Earth orbiting and the nominal interplanetary mission phases because of the low survivability of organics at impact speeds above about 20kms−1, a few 10s of interstellar particle detections with measurable organic compounds is predicted for the extended mission from 2028 to 2031.

 

References

Krüger, H., et al. (2019). Modelling destiny+ interplanetary and interstellar dust measurements en route to the active asteroid (3200) phaethon. Planetary and Space Science, 172:doi.org/10.1016/j.pss.2019.04.005.

Sterken, V. J., et al. (2013). The filtering of interstellar dust in the solar system. Astronomy and Astrophysics, 552:A130.

Strub, P., et al.  (2019). Heliospheric modulation of the interstellar dust flow on to Earth. Astronomy and Astrophysics, 621:A54.