1: Introduction.- 2: Charged-Particle Motion in Magnetic and Electric Fields.- 3: Trapping Region and Currents Due to Trapped Particles.- 4: Electric Fields.- 5: Wave-Particle Interactions.

Quantitative aspects of magnetospheric physics

The Loss Cone Imager (LCI) instrument is part of the US Air Force Demonstration and Science Experiments (DSX) satellite and is comprised of three components: the Fixed Sensor Head (FSH), the High Sensitivity Telescope (HST), and the Central Electronics Unit (CEU). The emphasis of this paper is on the FSH, which is comprised of three Si solid state detectors (SSD) each comprised of six pixels capable of measuring incident particle energies (~ 30 keV - 500 keV) and their respective pitch angles. The FSH is mounted onto the exterior of the DSX Payload Module and covers a 180° by
10° view of the sky. Each pixel has a 10° by 10° field of view. Due to a small geometric factor, the FSH is able to operate
in the high particle flux areas of the Earth's magnetosphere. The Readout Electronics for Nuclear Application 3 (RENA3) chip, developed by NOVA R&D, contains 36 analog channels used for detection of nuclear events. Each of the 18 Si pixels is connected to a corresponding RENA3 channel for event detection and analog energy readout. The output of the chip is digitized and the digital value of each event, along with its corresponding RENA channel, is recorded by the Data Processing Unit housed in the CEU.

Overview of the Loss Cone Imager Fixed Sensor Head Instrument

The High Sensitivity Telescope (HST) is a sensor comprising part of the Loss Cone Imager (LCI) on the DSXmission. The primary objective of the HST is to observe uxes of energetic electrons as small as 100 e cm 2 sr 1 s 1 within the Earths atmospheric loss cone. This is accomplished via a geometrical factor of 0 .1cm 2 sr combinedwith a collimator limiting the eld of view t o a 7 degree half-cone angle. The sensors are shielded to in order toreduce the background to levels permitting the detection of the stated ux. The HST will be looking for changesin this ux caused by events precipitating electrons into the atmosphere. Of primary interest are electronswith energies between 20 and 500 keV. The HST utilizes two fully depleted solid state detectors and threeanalog measurement chains. The primary detector is 1500 um thick and uses two measurement chains. A fastermeasurement chain for counting events at rates of 300k/sec and a slower measurement chain for measuring theenergy deposited by an event more accurately. The secondary detector is 1000 um thick and is used to detectevents that completely penetrate the primary detector. The analog electronics are built from discreet ampliers.Events on the faster primary chain are sorted into 5 energy bins. Events from the slow chain are digitized to8-bits of resolution.Keywords: Loss cone, magnetosphere, particle physics, solid state detectors, spacecraft instrumentation, wave-particle interaction

A high sensitivity telescope for measurements of energetic particles in the Earth's radiation belts

The Air Force Research Laboratory's Demonstration and Science Experiments (DSX) mission investigated wave‐particle interactions and the particle and space environment in Medium Earth Orbit (MEO) from June 2019 to May 2021. Its Wave‐Particle Interactions Experiment conducted over 1,300 active high power very low frequency transmissions in the radiation belts providing observations of antenna performance and signal propagation from a controlled source. This included hundreds of transmissions while in magnetic conjunction with other satellites. The Loss Cone Imager and Space Weather Experiment suite observed electron and proton populations over a wide energy range, with several of these instruments providing pitch‐angle resolution. The Space Environmental Effects Experiment investigated effects of the MEO environment on electronics and materials. The Adaptive Controls Experiment demonstrated technology for on‐board identification and control of large structure vibrational modes. We describe the DSX instrument capabilities and on orbit performance, science planning and operations for carrying out an array of active and passive experiments, and some initial results in brief. We also describe plans for further work and data release.

Overview of the Demonstration and Science Experiments (DSX) Mission

Ground Support Equipment (GSE) [1] is a versatile and multifunctional graphical user interface (GUI) and a
software/hardware platform. It is a custom-designed system executed in the LabVIEW programming language to serve
as an instrument health monitor for the Loss Cone Imager (LCI) satellite project. GSE mimics the behavior of the onboard
Experiment Computer System (ECS). Its functions comprise the measurement of voltage, current, and power, as
well as acting as a safety mechanism in case of any anomalous condition (e.g., over-current and/or over-voltage
situation). Individual log files record the sessions during which data is gathered and analyzed. Safety/warning alarm
flags shall be 'visible' from any individual window/tab. Analog-to-Digital Conversion (ADC) particle group
measurements will be displayed on six individual panels. GSE will be supplemented with a comprehensive user's
manual for added clarity.

Overview of GSE as a Multifunctional GUI

The Loss Cone Imager (LCI) will sample the energetic-particle pitch-angle distributions relative to the local geomagnetic field vector in the magnetosphere as a part of the Demonstration and Science Experiment (DSX) satellite. A description of the LCI electrical interfaces and data flow will be presented. The pitch angle and energy of energetic particles are recorded by the FSH (Fixed Sensor Head) and HST (High Sensitivity Telescope) sensor electronics using
solid state detectors. Energetic particle data must be extracted from the FSH and HST by the DPU (Data Processing Unit) and stored in a format that is practical for ground data analysis. The DPU must generate a data packet that is sent to the experiment computer containing science and housekeeping data, as well as receive ground and time commands from the experiment computer. The commands are used to configure the sensor electronics and change the data
acquisition periods of the science data. The instrument works in conjunction with the WIPER (Wave-Induced Precipitation of Electron Radiation) VLF (Very Low Frequency) transmitter on the DSX satellite to view the effects of VLF waves injected in the Earth's magnetic field on the precipitation of electrons into the Loss Cone. The system is designed to operate autonomously with the changing state of the transmitter to provide more appropriate data for examining the effects of the VLF transmitter.

Chad W. Parker

Papers

Loss cone imager digital system design