
IDEX Instrument
The IDEX instrument collects and analyzes interstellar dust and interplanetary dust particles found in our solar system to understand better their compositions, the speeds they travel, their concentrations within our solar system, and their interactions with the solar wind.
Interstellar dust are the small particles of solid matter that are believed to be formed from supernova star events that result in the formation of stars and planetary systems, including our very own. Interplanetary dust is similar but originates from comets and asteroids and is found between planets in a system.
Measuring the composition and velocity of these dust particles helps scientists understand what is found in the interstellar medium beyond, what can be found in the in-between spaces of our solar system, as well as what the heliosphere is made up of.
How It Works
A spring-activated door protects IDEX’s sensor head from contamination while it is being integrated into the spacecraft and during launch. In space, the door swings open permanently, allowing interstellar and interplanetary dust to flow into the instrument.
The collected dust passes through three sets of charged grids toward an impact target plate coated with pure gold. The grids prevent charged particles, electrons, and ions, from entering the instrument.
In a process called impact ionization, the dust crashes into the gold-coated target at a high speed, smashing the dust grains into their composite ions – tiny, charged particles. These fragments then spray upwards and are directed through an opening at the center of the gold target to a detector that counts the number of ions that are received.
The ringed structure surrounding the instrument and shield-like reflectron at the top of the assembly use electric fields to keep the ions from escaping and direct them towards the detector. This also works to form a simple time-of-flight (ToF) system by timing how long it takes the ion to reach the detector after impact ionization. Scientists use the amount of time and distance traveled from the target, up to the electric field and down to the detector to identify what elements the dust particles were made of. The heavier fragments (ions) of the dust move slower than smaller fragments, which means they are heavier elements such as iron and silicon. Faster ones are lighter elements, such as helium or hydrogen.
The final detector below the center counts the number of tiny dust particles collected by IDEX by measuring the amount of electrical charge they carry. Because space dust ions are so tiny, even a group of 1000 would not have a big enough charge for a sensor to pick up, so the charges need to be multiplied, or increased, to be detected.
This detector consists of a series of specially designed, electrically charged perforated disks, called dynodes, that have peaks and valleys surrounding each tiny hole. As the ions come through the opening in the middle of the gold target, they contact a peak of the disk that increases the ion’s charge and funnels it through the hole in the valley to the next disk where the charge is multiplied again as it meets the next peak. The ion is passed through the other disks like a pinball hitting bumpers, increasing its charge as it continues. By the time the particle reaches the final detector surface, the charge is large enough that it can be sensed and counted.
The impacts on IDEX’s gold-coated target leave a residue that can contaminate future collection of data. IDEX periodically on a previously set schedule heats up the target to high temperature that gets rid of this residue.
Explore the IDEX Model
Capturing StarDust
[This video has no sound.] Watch how IDEX captures stardust on the IMAP mission and uses it to understand better how life is possible on Earth.
How We Use IDEX Data
IDEX reveals the composition of the interstellar and interplanetary material locked in the dust grains. This helps gives scientists critical insight on the formation and evolution of matter both inside and outside our solar neighborhood. Composition data from IDEX also links the makeup of interstellar dust with the composition of interstellar neutrals (ISNs) and pickup ions (PUIs) measured by IMAP-Lo, CoDICE, and SWAPI.
Understanding the number of particles of space dust in a certain area of the sky, along with their composition, informs scientists how much of each type of elemental material is out there in various regions of our universe.
Meet the Team
IDEX was built and tested at the Laboratory for Atmospheric and Space Physics (LASP) at University of Colorado, Boulder under instrument lead Mihaly Horanyi.
Playing a role in the incredibly successful IDEX dust testing campaigns has been a highlight in my career. Testing like we fly required pushing the accelerator to its extremes for hypervelocity interstellar-like dust grains. The magnitude of IDEX and the team's precision was seen in all aspects, including using almost every inch of test chambers for this large instrument. Go IDEX, go IMAP!
- John Fontanese, Former IMPACT Dust Accelerator Operator, IDEX

The IDEX team together at UC Boulder-LASP after their Pre-Environmental Review (PER).
Image Credit: NASA/UCBoulder-LASP