The capturing ionospheric coupling and dynamic aurora (CICADA) nanosatellite mission concept

1 Introduction

Connecting visible auroral signatures to wave–particle interactions and the conditions that drive them is a compelling approach for understanding energy transfer from space to the Earth. Capturing Ionospheric Coupling and Dynamic Aurora (CICADA) is a nanosatellite mission concept (Figure 1) whose overall scientific goal is to “connect auroral forms to precipitating electrons energized by Alfvénic wave–particle interactions.” The CICADA instruments provide key measurements for determining how Alfvénic wave–particle interactions and field-aligned currents (FACs) link magnetospheric driving to ionospheric dynamics and auroras. The CICADA mission is also intended to flight-demonstrate a powerful Alfvénic wave–particle correlator technique for enabling future mission-of-opportunity-class investigations in the ∼4,500 km auroral acceleration region to definitively establish the in situ energy-transfer processes of Alfvénic auroras. We define the following three science objectives (SOs) that drive the CICADA mission and instrument design:

SO1: What fraction of a dynamic discrete arc aurora is associated with Alfvénic activity?

SO2: What fraction of the precipitating auroral electrons are causally related to Alfvén waves?

SO3: What is the relationship between the FACs and pulsating auroral patches?

Alfvén waves govern the coupling between the magnetosphere and ionosphere. Wygant et al. (2000) and Keiling et al. (2003) showed that there is (on average) a sufficient Alfvénic Poynting flux traveling Earthward to power the aurora. Spacecraft observation case studies have increasingly shown Alfvén waves magnetically conjugated to dynamic discrete auroral arcs (Chaston et al., 2006; Kataoka et al., 2021; Miles et al., 2018; Rother et al., 2007; Wu et al., 2020). Alfvén waves propagate energy through the magnetosphere–ionosphere (MI) system, and their reflection and/or resonance appear to provide feedback mechanisms to control/modulate the dynamics of MI coupling (Lessard and Knudsen, 2001; Lysak and Song, 2008). CICADA contributes directly to the Heliophysics Decadal Goal 2 of “understanding the dynamics and coupling of Earth’s magnetosphere, ionosphere, and atmosphere and their responses to solar and terrestrial inputs” by being the first mission to obtain all key measurements using a single spacecraft for quantifying the relationships among Alfvénic activity, precipitating electrons, and visible aurora.

CICADA will also contribute directly to the Heliophysics Decadal Survey Key Science Goals 2 and 4, i.e., solar and space physics: a science for a technological society (National Research Council, 2013). The wave–particle interactions probed by CICADA are at the heart of fundamental processes, such as waves, shocks, turbulence, and magnetic reconnections, that govern energy transport in and impact the evolution of many space plasma environments. Applying field–particle correlations to the CICADA measurements will contribute directly to the Heliophysics Decadal Goal 4 of “discovering and characterizing fundamental processes that occur both within the heliosphere and throughout the universe” by quantifying how Alfvén waves drive electron precipitations in dynamic auroras through wave–particle interactions.

2 Mission Science Objectives (SOs)

2.1 SO1: What fraction of dynamic discrete arc aurora is associated with Alfvénic activity?

Auroral acceleration has been broadly divided (Paschmann et al., 2003; Lühr et al., 2015; Mottez, 2015) into acceleration by quasistatic electrical potential (Evans, 1974) and acceleration by interactions with Alfvén waves (Lysak, 1990). Static discrete auroral arcs are traditionally related to kilo-electron-volt electrons accelerated by quasistatic electric fields (Swift, 1981), whereas Alfvénic aurora is more broadband (Chaston et al., 2003) and is associated with multi-arc (Trondsen et al., 1997) and small-scale dynamic (Stasiewicz et al., 2000) auroras. Wygant et al. (2000) and Keiling et al. (2003) showed that there was sufficient power in the Earthward Alfvén wave Poynting flux (at ∼6 Re) to power the aurora, hinting at the possibility of a systematic role. Miles et al. (2018) used an opportunistic conjunction between the enhanced polar outflow probe (e-POP; Yau and James, 2015) spacecraft (B, imaging) and Swarm (Friis-Christensen et al., 2008) spacecraft (B, E, n i) to demonstrate a technique for detecting Alfvénic activity coincident with an aurora. Figures 2a,b map e-POP’s location (pink circles) onto near-infrared (NIR) auroral images mapped to a 110-km emission height, and Figure 2c shows a comparison of the in situ magnetic waves Δ B (blue) with the auroral intensity at the conjugate foot point (orange).

Proving the Alfvénicity of the observed magnetic perturbations Δ B required additional knowledge of the electric field Δ E and plasma (ion) density n i through conjugate Swarm measurements. Figure 3a shows the interval immediately before auroral conjugacy, where no relationship is observed between the Δ E and Δ B measurements. However, as the spacecraft crosses the auroral arc (Figure 3b), both Δ E and Δ B show comparable perturbations.

Figures 3c,d show the calculated electric-to-magnetic-field ratios (Δ E / Δ B) as functions of frequency derived from the amplitude spectra of Δ E and Δ B. In the non-auroral region (Figure 3c), the noise in the electric field data is dominant such that the ratio does not converge to a physically meaningful value. However, in the auroral region (Figure 3d), the ratio oscillates near the local Alfvén speed at Swarm (V A = 1.4 × 10 6 m/s) for frequencies above ∼1 Hz. The Alfvén speed was estimated from the average ion density measured by the Swarm A Langmuir probe (LP) using V A = B / μ 0 ρ and by assuming that the ion density ρ is dominated by oxygen (Yau and Howarth, 2016). The Δ E / Δ B ratio at the Alfvén speed was predicted by Knudsen et al. (1990) for Alfvénic activity; this ratio would be flat for a single shear propagating Alfvén and oscillation with frequency about the Alfvén speed if a mixture of upgoing and downgoing waves exist owing to reflection from the ionosphere and/or the ionospheric Alfvén resonator (IAR). The ratio of the perturbations observed by Swarm/e-POP coincident with the dynamic discrete auroral arcs provides a diagnostic for the presence of Alfvén waves.

Recent high-resolution conjugate observations have demonstrated that Alfvénic processes contribute substantially to the dynamics, structuring, and energy deposition of discrete auroral arcs. Measurements combining in situ fields and particles with auroral imaging have shown that perpendicular plasma dynamics, including flow shears and magnetic tearing, drive energy transport with a spatial pattern that closely matches observed arc morphology (Chaston, 2024; Chaston, 2026). Desjardin et al. (2026) observed and modeled Alfvénic and inverted-V electrons sharing a common maximum energy; at the poleward edges of discrete arcs, Alfvén waves have been observed to modulate inverted-V electron distributions while generating filamentary auroral forms (Hirahara et al., 2024). Similar mixed acceleration signatures, including Alfvénic surges at substorm onset leading to or coexisting with inverted-V structures, have been documented during dynamic intervals (Hull et al., 2016; Motoba and Hirahara, 2016). These processes are often accompanied by evolving FACs and quasistatic potentials that interact with Alfvénic boundary activity (Hull et al., 2010; Marklund et al., 2011).

Complementary particle observations have provided detailed characterizations of the electron distributions within and around inverted-V structures, including their latitudinal dependences and relationships to the net energy and number flux (Dombeck et al., 2013; Dombeck et al., 2018; Fukuda et al., 2014). In particular, energy-dispersed electron signatures below typical inverted-V energies have been interpreted as evidence of resonant deceleration and acceleration by Alfvén waves (Chen et al., 2005). Such findings indicate that a significant fraction of the dynamic discrete arc aurora involves Alfvénic contributions or modulation, often operating alongside or at the boundaries of the quasistatic acceleration regions. Supporting numerical studies have further illustrated the underlying physical processes. Non-linear magnetohydrodynamic and gyrokinetic simulations of Alfvénic MI coupling have shown that feedback instabilities can spontaneously generate auroral structures, vortex formation, and a transition to turbulence with an associated energy cascade (Watanabe et al., 2025; Watanabe et al., 2026). Together, these observational and numerical results underscore the complexity of acceleration mechanisms in dynamic discrete arcs and highlight the scientific value of acquiring simultaneous high-cadence in situ measurements of the electromagnetic fields and precipitating electrons together with co-located auroral imaging, which are the central capabilities of the CICADA mission concept.

The CICADA instruments acquire all data required to determine the Alfvénicity of the magnetic perturbations using a single spacecraft, allowing it to be used on every auroral crossing. CICADA provides in situ E, B, and n i information with co-located auroral imaging. The imager must resolve the ∼1 km structure of the dynamic discrete auroral arc dynamics with the available field of view (>100 km) and cadence (>0.5 Hz) to capture the mesoscale morphology of the aurora around the magnetic footprint. The magnetometer (MAG) must resolve the approximately 1–20 nT signatures of the Alfvén waves at sufficient cadence to capture the dominant 1–15 Hz local Alfvénic range. The electric field instrument (EFI) must resolve the approximately 1–20 mV/m component at the same 1–15 Hz cadence. The LP must provide the local plasma (ion) density for estimating the local Alfvén speed. These measurements are all provided by instruments with recent sounding-rocket heritage.

CICADA’s dataset will enable additional analyses beyond this proposal to address other significant science questions. For example, the Knudsen et al. (1990) argument that the Δ E / Δ B ratio for static currents is controlled by the ionospheric height-integrated Pedersen conductivity Σ p but that for Alfvén waves tends toward the Alfvén speed V A and will alternate between 1 / Σ p and μ 0 V A Σ P as a function of frequency (e.g., Figure 3d) can be tested with the ground-based Σ p. Similarly, the data could be examined for evidence that the waves are modulated by the IAR, similar to electron acceleration in the IAR suggested by Chaston et al. (2002b) or the IAR trapping of Alfvén waves emitted by a flow-shear-driven instability (Asamura et al., 2009). For a single traveling Alfvén wave, the Δ E / Δ B ratio is given by the local Alfvén speed V A (Knudsen et al., 1990; Burchill et al., 2004). The separation between the frequency peaks in the impedance spectrum is theorized to be set by the electrical length z / λ between the ionospheric reflection and observation. CICADA is also ideally suited for examining IAR-modulated suprathermal electron bursts (Wu et al., 2021), the occurrence of Alfvén waves relative to single/multiple FACs (Wu et al., 2020), and the importance of Alfvén waves for MI coupling (Pakhotin et al., 2018).

2.2 SO2: What fraction of the precipitating auroral electrons are causally related to Alfvén waves?

Precipitating electron measurements (Chaston et al., 2010; Kataoka et al., 2021) provide a critical means to distinguish between an aurora from inverted-V potentials (discrete auroral arcs) (Frank and Ackerson, 1971; McIlwain, 1960) and a small-scale dynamic aurora driven by Alfvén-wave-accelerated electrons (Stasiewicz et al., 2000). Directly correlating the electromagnetic field measurements with the electrons is a powerful tool for establishing a causal relationship between the precipitating electrons and waves responsible for their acceleration. Early demonstrations of on-board wave–particle correlator instrumentation on sounding rockets and spacecraft have successfully allowed detection of electron phase-bunching in intense Langmuir waves (Ergun et al., 1991; Kletzing et al., 2005) and energy transfer between energetic electrons and whistler-mode chorus emissions (Katoh et al., 2018).

A new theoretical formulation of this approach called the field–particle correlation technique (Howes et al., 2017; Klein et al., 2017; Klein and Howes, 2016) has recently led to significant scientific discoveries. Applications to kinetic numerical simulations have shown that Landau damping (Conley et al., 2023; Klein et al., 2017), transit-time damping (Huang et al., 2024), and cyclotron damping (Klein et al., 2020) are effective at dissipating weakly collisional plasma turbulence, while demonstrating a feasible observational means of partitioning the energy between plasma heating and particle acceleration in collisionless shocks (Juno et al., 2023). Application to the magnetospheric multiscale (MMS) mission provided the first direct measurements of electron Landau damping (Afshari et al., 2021; Chen et al., 2019) and ion cyclotron damping (Afshari et al., 2024) that removed energy from turbulence in the Earth’s magnetosheath and has helped identify the velocity-space signature of shock-drift acceleration at a perpendicular region of Earth’s bow shock (Montag et al., 2025).

Sounding-rocket measurements of dynamic auroras precipitating time-dispersed electrons, with higher-energy electrons arriving before lower-energy ones, have long been attributed to acceleration by the Earthward-propagating Alfvén waves (Kletzing and Torbert, 1994). The concept that dispersive Alfvén waves can support parallel electric fields capable of accelerating auroral electrons was developed in the pioneering theoretical works of Hasegawa (1976) and Goertz and Boswell (1979). The strong magnetic field and low plasma density of the auroral magnetosphere leads to an Alfvén wave velocity that is higher than the electron thermal velocity and denotes the inertial Alfvén wave regime (Stasiewicz et al., 2000). Lysak (1990) showed that Alfvén waves with perpendicular wavelengths around the plasma skin depth, k ⊥ d e ∼ 1, generate a parallel electric field that can resonantly accelerate electrons toward the Earth. The time-of-flight analysis of these dispersed electron signatures typically places the acceleration at an altitude of 2,000–6,000 km (Andersson et al., 2002; Kletzing and Hu, 2001; McFadden et al., 1986; Paschmann et al., 1983; Tanaka et al., 2005).

Future applications of the field–particle correlator to spacecraft measurements (Howes et al., 2022; Verniero et al., 2021) within the acceleration region at 2,000–6,000 km can be used to demonstrate the acceleration of electrons by the parallel electric field of the inertial Alfvén wave, as demonstrated in laboratory experiments (Schroeder et al., 2016; Schroeder et al., 2021). The precipitating electrons at CICADA’s 400–600 km altitude are no longer resonant with the slower Alfvén waves in the dense ionospheric plasma; however, postprocessed correlations between electron arrival and the associated downward-propagating Alfvén wave flux can be employed to achieve the goal of SO2 as follows. A 500-eV beam of electrons accelerated at 5,000 km will reach an altitude of 500 km within 0.35 s. The slowing Alfvén wave will require approximately twice this time of approximately 0.70 s. The spacecraft moving at ∼7.6 km/s will have traversed 2.6 km during the delay between the particle and wave arrivals. Sounding-rocket measurements of the downward Poynting flux of the Alfvén waves tend to span distances of ∼10 km (Andersson et al., 2002; Arnoldy et al., 1999; Feltman et al., 2025; Kletzing and Torbert, 1994). CICADA establishes a causal relationship by correlating the arrival of the precipitating electrons with that of the subsequent Alfvén waves. Modeling the electron trajectory and Alfvén wave propagation (using models of the altitude profiles of the electron density, ion composition, and magnetic field) would enable statistical determination of the causal relationship between the Alfvén waves and accelerated electrons, thereby achieving SO2.

A new simulation has been developed for inertial Alfvén wave propagation along high-latitude auroral field lines to assist in back-correlating CICADA’s future measurements of waves and particles. The simulation uses the Liouville mapping technique demonstrated by Kletzing (1994) to generate electron plasma distributions for a chosen altitude along the geomagnetic field line over a range of observation times. Here, the altitude dependence of the nightside plasma density (Chaston et al., 2002a) and dipole magnetic field strength are used to produce realistic distributions relevant to future CICADA observations, instead of the homogenous plasma environment used by Kletzing (1994).

The top two panels of Figure 4 show the observed electron flux as would be observed by CICADA’s electron detector for three runs at illustrative altitudes. Here, the electron plasma distributions are generated using a fourth-order Runge–Kutta (RK45) solver in velocity space identical to Kletzing (1994), with an assumed background Maxwellian plasma sheet distribution having n = 0.25 c m − 3 and Te = 120 eV at every altitude. For each velocity-space point, the electron motion is solved under the influence of the mirror force and parallel electric field of the wave in one dimension, namely, along the geomagnetic field line in modified dipole coordinates (Kageyama et al., 2006). The simulated velocity-space grid and temporal resolution are identical to those of the CICADA electron electrostatic analyzer. Both the simulation and electron energy and pitch angle analyzer (eEPAA) use 49 logarithmic energy steps from 10 eV to 10,000 eV at 19 pitch angles in the range of 0 < α < 180° and are sampled every 50 ms over 0 < t < 10 s. Once the distribution functions are generated, they are converted to differential energy flux via the relation J E = 2 E 2 m e 2 f t , v ⊥ , v ∥. The initial conditions of the simulated inertial Alfvén wave are set to f = 8 Hz, with a perpendicular wavelength of 2.5 km at z 0 = 500 km and Earthward propagation starting from 20,000 km with an initial perpendicular potential of Φ⊥ = 250 V. The bottom six panels of Figure 4 show the plasma environment and resulting E_⊥ and E_∥ for this configuration. Wave propagation was solved using the RK45 method and the plasma ray equations under a Wentzel–Kramers–Brillouin (WKB) assumption to determine k ⊥ t , k ∥ t , x → t for a set of initial x 0 → , k ⊥ , 0 , k ∥ , 0 at z0.

In this simulation, the ambient plasma sheet electrons are observed to evolve from an isotropic distribution into a field-aligned beam, which is clearly resolved in the simulated CICADA electron flux data at the top of Figure 4. The parallel electric field of the wave is first observed to perturb the ambient distribution at 10,000 km near t = 2.9 s, then continue acceleration at 5,000 km and t = 3.4 s up to 1 keV. By the time the wave reaches 500 km, enough time has elapsed to time-disperse all electrons, and the wave resonance has ceased because of damping of the parallel electric field of the wave due to the diminishing inertial effects.

An identical process is revealed in Figure 5, but in greater detail, showing the full velocity-space signatures for these bursts and the use of the field–particle correlation technique that will be key to CICADA SO2 closure. At 8,000 km and t = 3.2 s, the high-energy electrons exiting the front of the wave are observed near v ∥ v t h , P S = 2, where v ∥ is the electron parallel velocity and v t h , P S is the thermal velocity of the plasma sheet electrons. These energies fall above the line representing the local inertial Alfvén phase velocity of the wave (solid black line) but below the maximum resonant electron energy (dotted black line). At 8,000 km, the cutoff between the resonant and non-resonant electrons is clearly observed at t = 3.3 s since any electrons that fall within the resonance lines appear to be “snipped off” from the distribution and carried by the wave. Conversely, a similar phenomenon does not occur at 500 km since the resonance window for the wave shrinks dramatically near 500 km. These results are consistent with the model by Kletzing (1994) but are now applicable to a more realistic plasma environment.

One of the chief interests of the CICADA mission is estimating the energization process between the waves and particles over the same altitude ranges. Applying the field–particle correlation technique to the simulation would estimate the work done on the particles by the local wave fields via joule heating (J⋅E). The bottom panel in Figure 5 shows the calculated total field–particle correlation values for several altitudes spanning 500 km < z < 20,000 km; these values are generally consistent with the picture that inertial Alfvén waves deposit most of their energy into plasma acceleration between 2,000 km and 10,000 km. For a given CICADA dataset of electric/magnetic waves and particles, inexpensive simulations such as these can be performed in reverse under different plasma environments (e.g., dayside, active auroral, and nightside) to tease out the likely Alfvénic processes that occurred and characterize if their energization profiles are realistic. However, CICADA is uniquely able to correlate specific wave observations to particle measurements more definitely, which improves the modeling effort by ensuring that the correct input parameters are chosen.

The dominant Alfvén wave energy flux falls within 1–15 Hz (Feltman et al., 2025), and the techniques of SO1 using CICADA measurements of n i, Δ B, and Δ E will help identify the downward Alfvén wave energy flux. The precipitating electrons are measured by the eEPAA, and each pass through an active aurora is identified by the fast auroral imager (FAI) using the methods of SO1. The downward Alfvén wave energy flux and precipitating electron measurements are transmitted to the ground and correlated in time with a lag since the acceleration occurs above CICADA’s orbit. The combined electric and magnetic field spectra enable determination of how the turbulent wave energy fluxes deposit energy in the ionosphere (Di Mare and Howes, 2024), as illustrated in Figure 6. CICADA’s measurements of fields up to 128 Hz, along with the estimated instrumental noise floors indicated in Figure 6, provide valuable new constraints on how plasma turbulence mediates coupling between the magnetosphere and ionosphere, in addition to achieving SO2. For example, a recent analysis of the TRICE-2 sounding-rocket measurements showed the partitioning of the dissipated turbulent energy between ions and electrons (Di Mare and Howes, 2024).

2.3 SO3: What is the relationship between the FACs and pulsating auroral patches?

Much progress has been made in recent decades on the source regions of pulsating auroras. Chorus waves in the equatorial magnetosphere scatter electrons into the loss cone in a quasiperiodic fashion, thereby producing the pulsating patches observed in the ionosphere (Jaynes et al., 2013; Kasahara et al., 2018; Nishimura et al., 2010). A recent work uncovered details about this process, including the extent of energy involved in the precipitation (Miyoshi et al., 2020). Pulsating auroras are now known to affect middle atmospheric chemistry, such as the ozone concentration (Verronen et al., 2021). The electrodynamics of precipitation patches in pulsating auroras remains ill-defined. The existence of FACs at the edges of or between the pulsating patches was posited by Oguti and Hayashi (1985). FACs are crucial to the two-way coupled MI system. Pulsating auroras are ubiquitous (Oguti et al., 1981) and can be widespread and long-lasting (Jones et al., 2011; Jones et al., 2013), thereby contributing significantly to the overall electrodynamics of the coupled MI system. The FAC structure and polarization electric fields created within the patch itself can cause ionospheric feedback to affect the magnetosphere system, possibly leading to structuring of the cold plasma within the equatorial magnetosphere, which is poorly characterized for small spatial and temporal scales. The observed parallel electric fields that are co-located with the pulsating aurora may be sufficient to influence plasma outflow from the ionosphere (Liang et al., 2021). Only a handful of studies have been able to explore the FAC aspect of a pulsating aurora. Figure 7, sourced from Nosé et al. (2024), summarizes the results of each limited-range study, where “present study” indicates the results obtained by Nosé et al. from the 2022 LAMP sounding rocket.

Fujii et al. (1985) examined overflights of the MAGSAT spacecraft while a pulsating aurora was observed in conjugate all-sky imagers; they found enhanced FACs on the boundaries of the patches that occurred in pairs of sheet-like currents and hypothesized that the conductivity enhancement within the patch led to current closure by the FACs at the patch boundaries. Twenty years later, Sato et al. (2004) investigated a conjunction between the FAST spacecraft and a pair of interhemispheric conjugate ground-based all-sky imagers. Both missions observed pulsating auroras and weak FACs not at the edges of the patches but somewhere in the middle; it is not clear why these two missions only resulted in limited conjugate observations of pulsating auroral FACs. However, it is notoriously difficult to obtain clear all-sky images at the precise time of a short low-altitude overflight. CICADA’s onboard imager operates irrespective of cloud cover and allows checking the FAC algorithm for errors due to non-orthogonal crossing (Forsyth et al., 2017).

Gillies et al. (2015) reported the most compelling spacecraft study thus far; they inferred the j ∥ of the FAC from the in situ cross-track magnetic field B y and along-track spacecraft velocity V x using the relation j ∥ = 1 μ 0 1 V x d d t B y. They observed multiple pairs of FAC sheets within a single patch that occurred both inside and at the edge of the patch. Their dataset comprised nine passes of the Swarm spacecraft over a pulsating aurora crossing poleward across the patches (or vice versa). Figure 8 shows that strong FACs were observed at the boundaries of two patches while weak FACs were observed within these patches. The FACs were always observed adjacent to at least one side of the patch (usually poleward). The most recent observations are from the 2022 LAMP sounding-rocket mission. Nosé et al. (2024) used an in situ magnetic data conjugate to an energetic pulsating aurora and found a classic down/up FAC sheet pair on the equatorward/poleward edge of a patch, which is in agreement with the current closure model results of Oguti and Hayashi (1985) and Fujii et al. (1985).

Clearly, it is an unsolved question whether FACs only appear in sheet pairs on the north–south edges of patches. Is this phenomenon only true for very regular and elliptical patches? What happens with elongated patches that occur in a thin north–south alignment or in irregularly shaped patches? What are the typical values of the FACs and, if they are ubiquitous, how much do they contribute to plasma outflow from the ionosphere to the magnetosphere? CICADA is designed to answer these questions and thereby deliver novel insights into the electrodynamics of pulsating auroras and the complete ionosphere–thermosphere–magnetosphere system.

2.4 Data sufficiency

CICADA’s mission duration is defined by the time required for robust sampling of a range of geomagnetic conditions and substorm intervals within nightside observing conditions. Substorms occur at the rate of once every 2–4 h, and a reasonable range of geomagnetic conditions occurs within a period of several months. To achieve a statistically significant database of events, the baseline mission duration is 6 months. Similarly, if a polar orbit were available, a 6-month mission would allow sampling of all local times during orbital precession.

2.5 Mission success criteria

Baseline mission success can be achieved by addressing SO1, SO2, and SO3. The mission design provides a scientifically robust dataset averaging more than 50 region-of-interest crossings per week. The intended 6 months of operations can provide a statistically representative sampling of the relevant range of geomagnetic conditions. The threshold mission success can be achieved by answering at least one of the SOs. Table 1 demonstrates that the threshold mission can be achieved even with some instrument failures.

TABLE 1. Instruments involved in closing each science objective (SO).

3 Mission implementation

CICADA’s payload (Figure 9) comprises a robust in situ plasma package with co-located auroral imaging. The spacecraft is three-axis stabilized and executes a preprogrammed pitch maneuver to match a model-predicted magnetic field during observations. The 3D in situ magnetic field is measured using the MAG on a 60-cm deployable boom. The 2D in situ AC electric field is measured using two pairs of Stacer booms (for the EFI) that deploy to a 2-m tip-to-tip separation and are oriented perpendicular to the background magnetic field. The in situ plasma density is inferred from the ion density measured using the LP. The precipitating electrons are measured using the eEPAA that is oriented parallel to the magnetic field for measuring pitch angles of 0°–180°. The auroral intensity is obtained using the FAI pointed along the magnetic field in the downward direction.

3.1 Instrumentation

3.1.1 Magnetic field instrument (MAG)

The MAG comprises two fluxgate sensors arranged in a gradiometer on a deployable boom with heritage to the MAGIC technology (Miles et al., 2025a) demonstration on the TRACERS Small Explorer (SMEX) mission (Miles et al., 2025b). The next-generation MiniT sensor (Figure 10a) is derived from MAGIC’s Tesseract sensor (Greene et al., 2022; Greene et al., 2024) and is simpler, more compact, and provides equal or better performance for mass, power, volume, magnetic noise, and offset. A single electronics package (Figure 10b) is used to drive and digitize both sensors.

The fluxgate MAGs (Primdahl, 1979; Snare, 1998) sense the magnetic field via the electromagnetic force (EMF) induced by the changing magnetic flux; their performances are limited by the intrinsic magnetic noise of the ferromagnetic cores as they enter magnetic saturation. The MAG uses custom permalloy racetrack geometry cores (manufactured at the University of Iowa) that reproduce the performances of the historically used legacy Infinetics S-1000 ring cores from the 1960s. The manufacturing process is well documented (Miles et al., 2019; Miles et al., 2022) and gives ∼90% yield for the cores with noise better than 5 pT/√Hz at 1 Hz (Narod and Miles, 2024). This capability to manufacture custom miniature fluxgate cores enables the nanosatellite-scale MiniT sensor used here. This hardware has been flown successfully on the ICI-5b sounding rocket in 2026.

The MAG is vector calibrated (Broadfoot et al., 2022) at the Iowa 2-m Merritt coil facility to transform the raw sensor data (E, in engineering units) to fully calibrated vectors in the spacecraft common reference frame (B C R F, in nT). This corrects any errors in the offset (b), sensitivity (S), orthogonality (P), and rotation (R A determined pre-flight and is then trended via in situ calibration as

B C R F = R A − 1 P − 1 S − 1 E − b .

The calibration also corrects for the minor non-linearity of each channel, weak dependency of gain on sensor temperature, and weak dependency of instrument zeros on electronics temperature.

3.1.2 Deployable MAG boom

The two MiniT sensors are deployed away from the magnetic noise of the spacecraft using the 60-cm BLAZE non-magnetic boom (Figure 11) developed by the University of Iowa with funding from NASA’s SpaceTech-REDDI program. The boom is stowed outside the spacecraft in the interstitial space within the dispenser (Figure 18), with the sensors pocketed back into the spacecraft volume.

The boom uses non-magnetic materials and is deployed using phosphor bronze springs. A ramp pin detent system provides repeatable positional accuracy, deployment speed control, and over-travel adjustment while locking the boom once it reaches 180°. Reliable and repeatable deployment was demonstrated through numerous tests in simulated microgravity via parabolic flights (Figure 10b) on a B727-200 aircraft. The stowed boom is retained by an EBAD FC2 size Frangibolt®; during commissioning, redundant firing circuits in the EBAD Frangibolt® actuator fracture the Frangibolt® to initiate deployment.

3.1.3 Magnetic noise mitigation

Traditionally, stray spacecraft magnetic fields are controlled through a strict magnetic cleanliness plan (Miles et al., 2026). However, CICADA uses the MAGSTAR software suite (Finley et al., 2023b; Finley et al., 2023a) developed in part for TRACERS (Miles et al., 2025b) to mitigate the residual noise at the boom end. MAGSTAR combines statistical signal processing and machine learning driven by the gradient between the two sensors [e-POP and Parker solar probe (PSP)] to mitigate local interference by ∼90% (Figure 12). MAGSTAR does not rely on physics-based models or housekeeping data. The combination of a deployable boom, a gradiometer, and signal processing provides robust magnetic data without imposing costly magnetic controls on the other instruments or the commercial nanosatellite.

3.1.4 Electric Field Instrument (EFI)

The EFI comprises four voltage probes (two pairs) providing the 2D electric field orthogonal to the magnetic field when crossing the aurora. The probes maintain a floating potential while a bias current is applied to match the ambient plasma. The electric field is derived from the potential difference between the two antiparallel probes divided by the effective length between them. A programmable current source is applied to each of the four probes through a series resistor. The differential voltage across the resistor is measured using a low-input-current amplifier and gives the probe current. The differential voltage across a pair of probes is obtained with a second amplifier and a programmable resistor network. The two differential voltages and four probe currents are simultaneously digitized at 16-bits and sent to the spacecraft. Each probe is mounted on a 1-m boom stowed within the spacecraft body during launch (Figure 13a) and is deployed on-orbit during commissioning (Figure 13b). The booms are machined from PEEK plastic tubes (filled to 30% with carbon fiber for conductance) with mechanical restraining features to constrain the maximum extension. Each boom is actuated by a small servo motor; a spur gear on the motor shaft drives a flexible nylon rack gear running through the inside of the boom and is attached to the smallest (tip) element and the spherical probe. One version of this boom design was used on the 2024 RockSat-X mission (Figure 13).

The rack gear is stowed for launch by spooling inside a circular containment enclosure (Figure 13c); this rack gear is uncoiled by the servo during deployment by pushing out the smallest boom element, which progressively pulls out the larger elements until the boom is fully extended. Deployment completion is detected by the stall current of the motor. The motor provides sufficient torque to both extend the boom and establish its stiffness. The wire connecting the probe to the electronics is accommodated by a slot in the rack gear. Each of the four voltage probes in the EFI has an individual preamplifier, and these are connected to a single electronics box (Figure 13d). The sensor, preamplifier, and electronics box are calibrated and tested both individually and together to measure the frequency response, noise floor, sensitivity, dynamic range, and applied bias current. The calibration procedures are adapted from those used successfully on the TRACERS, PSP, and MMS missions.

3.1.5 eEPAA instrument

The eEPAA is an electrostatic hemispherical charged-particle imaging device based on the original design by Carlson et al. (1982); it counts single electrons that have a selectable energy range and a velocity vector lying within a specific azimuth plane. The instrument provides high-time-resolution measurements while retaining excellent energy coverage. This is crucial for accurate determination of the variation in electron distributions in the auroral region, which can vary over short scales of ∼500 m (∼65 ms). The basic design of the eEPAA (Figure 14) is identical to those flown on several suborbital rockets, including ACES (2009), CHARM II (2010), TRICEII (2018), CAPER II (2019), and ACES-II (2022), and is very similar to that of the ACE instrument (Halekas et al., 2025) on the TRACERS SMEX mission (launched in 2025). The 10 × 10 × 15 cm design of this instrument has been specifically engineered for a nanosatellite.

CICADA pitches the spacecraft to align the background magnetic field within the aperture plane in the region of interest, so all upgoing and downgoing pitch angles are sampled simultaneously. Microchannel plates are used to amplify the charge deposition, followed by an array of charge-sensitive amplifiers. The University of Iowa detector employs twenty-one 10° active anodes spaced evenly around a 210° azimuthal field of view centered at the 90° pitch angle. The energy values are stepped at a cadence of 1.25 ms. The sensor sweeps from high to low energies in 48 steps, accumulating the values for 1.1 ms during each step; considering the dead time for the retrace back to the highest energy, one full energy sweep takes 62.5 ms. Each sweep covers the energy range of 20–10,000 eV with a 15% fractional resolution; this is better than the 18% intrinsic resolution of the instrument and ensures that there are no gaps where narrow features in the electron distribution could be missed. Typical auroral region fluxes produce good count levels with accumulation intervals of 1.1 ms and a per-pixel geometric factor of 8.63 × 10 − 5 c m 2 sr e V / e V. This enables rapid determination of the particle spectrum.

The eEPAA is calibrated in the calibration chamber at the University of Iowa. The chamber implements a UV-backlit chromium surface to produce a very cold beam of electrons (<1 eV thermal spread). The chromium surface is biased at a set potential that accelerates the electrons toward the sensor across a uniform potential. The energy of these electrons can be stepped from 1 eV to 10 keV. In the chamber, the sensor is mounted on an actuated platform that is rotated both azimuthally and poloidally; this allows the sensor to be stepped through all energies and look angles, providing full characterization of the sensor response to a uniform flood of electrons in terms of the energy and incident angle (Lessard et al., 1998).

3.1.6 Fast Auroral Imager (FAI)

The FAI uses an Owl 1280 flight-ready camera from Raptor Photonics. Following the e-POP NIR example in Figure 2, CICADA is baselined to image at 650–1,100 nm (primarily N 2 , O 2 , a n d N 2 +, where the short radiative lifetime allows the emissions to track the dynamic variations of the precipitating particles (Cogger et al., 2014). A formulation phase trade study will consider the relative merits of imaging the visible spectrum; here, the cadence, exposure, and resolution are balanced to capture both the mesoscale context of a dynamic discrete arc aurora and its fine elements. A cadence of one image per second can capture the auroral dynamics. The Owl 1280 captures highly sensitive monochrome images at 10-bit depth, providing auroral images while the spacecraft is fully eclipsed. The FAI uses the imager’s maximum high-gain exposure of 82 ms, which at the spacecraft velocity of ∼7.6 km/s can skew a source of ∼625 m and set the minimum spatial resolution. The 30°-field-of-view lens and an assumed 110-km emission give a swath of ≥150 km at orbit altitudes ≥400 km (Figure 15). Accordingly, the imager’s native 1280 × 1024 InGaAs detector output is binned on-orbit to 320 × 256 to fully resolve the minimum spatial resolution but increase the signal-to-noise ratio by ∼ 4 × for an effective ∼12-bit sensitivity.

The Owl 1280 flight-ready camera is a compact low-resource instrument occupying less than 2U of volume. CICADA orients the spacecraft to point this camera in the downward direction along the magnetic field in the region of interest. The imager has an active area of 12.8 × 10.24 mm and a dark current (e/p/s) of <19,000 at 15 °C, which is sustained by an active thermoelectric cooler (TEC). This allows the camera to form images with an 82-ms exposure to preserve the details of the dynamic arc structures. The camera is purchased in the fully calibrated condition with all coefficients preloaded for non-uniformity correction. This corrects each image sensor pixel level for offset, gain, and dark current using correction maps that have been created and stored for each camera during acceptance testing at a stabilized sensor temperature of +15 °C. The high-speed low-voltage differential signaling (LVDS) CameraLink Base interface transfers the raw images to the spacecraft in real time when examining the region of interest for later processing and downlink.

3.1.7 Langmuir Probe (LP)

LPs are routinely used on sounding rockets and spacecraft to measure the in situ plasma density (Barjatya et al., 2009; Brace, 1998). They can be implemented as fixed-bias (DC) probes or be swept for bias with respect to the spacecraft chassis ground. Swept-bias probes provide absolute plasma density and electron temperature values with every sweep; however, they can swing the floating potential of the spacecraft on a nanosatellite (Barjatya et al., 2013; Szuszczewicz, 1972). A fixed-bias LP measures the collected current at a fixed potential in the electron- or ion-saturation region where the current is directly proportional to the plasma density.

Planar LPs have relatively flat current collection characteristics in the saturation regions. Small changes in the applied bias due to the fluctuating floating potential have little to no impact on the saturation region collection current. When biased negative in the ion-saturation region at orbital velocities, the ram collection current for ions is about ten times larger than the thermal ion current. The orbital velocity and ram cross-section of the planar probe can be used to transform the measured current into the absolute ion density and small-scale dynamics. The planar LP is necessarily placed on the ram face of the spacecraft; this technique tolerates the <20° pointing error resulting from pitching the spacecraft to the magnetic field. Even a 30° pointing error results in only a 15% drop in collection area, which can be fully recovered by calibration since the pointing is known to an accuracy of ≪ 1 °. The LP is meticulously calibrated against a National Institute of Standards and Technology (NIST)-calibrated sourcemeter that provides currents spanning the entire range of the LP electrometer. This gives the relationship between the count digitizer and input current in amperes. This calibration is conducted over the LP’s full operational range of −35 °C to +65 °C in a thermal chamber to account for temperature-based changes in the LP electrometer performance.

The LP has a direct heritage to the LLITED dual nanosatellite mission currently operating nominally on-orbit. The planar ion probe sensor on the nanosatellite (Figure 16) is 4.6 × 6.6 c m and includes a 1 − c m-wide guard band with a 1 − m m gap. The sensor is biased at − 7 V relative to the spacecraft chassis, placing it robustly in the ion-saturation region. The probe is gold-plated to better withstand the atomic oxygen environment of the low Earth orbit. This LP measures densities in the range of 2 × 10 2 to 2 × 10 6 c m − 3 with a resolution of 2 × 10 2 c m − 3. Although this LP can sample up to 40 kHz, it is limited to 256 samples per second for CICADA.

3.1.8 Benefits and broader impacts

Among the fundamental plasma processes that govern the evolution of heliospheric plasmas, including waves, turbulence, shocks, and magnetic reconnections, only the electric field affects the plasma particles. Hence, nanosatellite electric field measurements would enable studies on plasma heating and particle acceleration in heliospheric plasmas governed by these fundamental processes. Unfortunately, nanosatellite EFIs have historically been extremely difficult to implement. A three-axis-stabilized nanosatellite requires rigid booms to hold the probes at sufficient distances for sensing and for separation from the electrical influences of the spacecraft. These booms often require more volume than typical nanosatellite plasma instruments. The CICADA mission will demonstrate a robust and cost-effective telescoping boom that will make electric field instrumentation available to a broad range of applications while greatly enhancing the scientific output of nanosatellites. A prototype of the EFI implementing updates from the prior sounding-rocket version has been fabricated and tested prior to the EFI flight build, providing the technology maturation shown herein.

Although a complete non-gyrotropic pressure tensor requires gyrophase-resolved 3D distributions beyond the scope of the proposed 16U three-axis-stabilized pathfinder, the calibrated energy vs. pitch angle measurements from the eEPAA still enable derivation of the parallel energy flux and application of the field–particle correlation technique. These data products will support community investigations of kinetic processes, including the energy transport, instability, and particle transport aspects in the auroral ionosphere. Correlating CICADA’s electric field data with particle measurements will provide a direct measure of the energy transfer between fields and particles (Klein and Howes, 2016; Chen et al., 2019), offering a powerful new approach to quantify how magnetospheric disturbances driven by the varying solar wind couple their energy to the ionosphere.

CICADA is an enabling pathfinder for a future mission with an on-board Alfvénic field–particle correlator to probe the auroral acceleration region in situ at 4,000–6,000 km. This will allow direct measurement of the acceleration of electrons at the spacecraft position, thereby validating laboratory results (Schroeder et al., 2021) and providing an in situ quantitative confirmation of the role of Alfvén waves in generating dynamic auroras. CICADA paves the way for a future mission to directly sample the auroral acceleration region and could definitively establish the proposed causality of Alfvénic auroral electron acceleration through wave–particle coupling via direct in situ measurements. Such a mission offers a vastly higher impact science but is significantly more challenging technically. The spacecraft would need to operate around an altitude of 4,000–6,000 km, which requires either a dedicated launch, a separate spacecraft (a “tug”) to help raise the orbit, or significant on-board propellants. These altitudes accumulate significantly more radiation (total integrated dose and single event effects), which pose challenges for commercial off-the-shelf nanosatellite spacecraft hardware. Such orbits are also not natural graveyard orbits, so the spacecraft would likely require some means of accelerated de-orbiting at mission end. This level of complexity makes a mission to directly sample the auroral acceleration well suited to a NASA mission of opportunity or Pioneers scale funding opportunities.

The CICADA auroral imager offers opportunities for outreach and public engagement around heliophysics and space weather research. The traditional tractable scope and simple implementation of a nanosatellite mission can be highly effective anchors for outreach and education (Ferrari et al., 2018). High-resolution images and movies of dynamic auroras provide visually compelling content that can be shared via social media and can attract a large and highly engaged following (MacDonald et al., 2015). Missions such as SMILE (Carter et al., 2025) have successfully incorporated auroral imagery into their outreach programs. Similarly, CICADA’s auroral imager can provide awe-inspiring visuals and local aurora observations as a space-based imager to communities that may not have an existing ground-based all-sky auroral imaging system.

3.2 Spacecraft and accommodation

CICADA is implemented as a 16U commercially procured nanosatellite launched into a nominal 400–600 km noon–midnight sun-synchronous circular orbit via a commercial rideshare. If available, a polar orbit would provide additional science returns. The instruments are built by their respective teams, with project management and system engineering oversight from the University of Iowa. The FAI camera and optics are purchased from Raptor Photonics. The complete instrument suite is integrated and environmentally tested at the University of Iowa before being delivered to the spacecraft as a prequalified instrument suite. The spacecraft, nanosatellite dispenser, launch-site integration, access to space, spacecraft commissioning, and on-orbit operations are all procured commercially. Table 2 summarizes the key mission parameters.

TABLE 2. Payload summary table.

CICADA uses a standard commercial spacecraft without customization beyond apertures in the face sheets for deployables and instrument fields of view. The spacecraft avionics occupy the 4U volume adjacent to the solar panel mount points, leaving 12U of volume for the instrument payload. The four EFI booms are deployed in two offset planes orthogonal to nadir–zenith (Figure 17a) to measure the 2D electric field perpendicular to the background magnetic field in the region of interest. These EFI booms are clocked 30° to the spacecraft coordinates to avoid the plasma wake of the deployed solar panels. The LP patch antenna is mounted on the ram face (Figure 17b), which positions it within 20° of the spacecraft ram direction throughout the region-of-interest pitch maneuver to track the magnetic field. Accurate knowledge of the spacecraft attitude is required to ensure alignment of the eEPAA aperture with the background magnetic field (for ensuring correct pitch angle determination) and to map the magnetic footprint to the FAI’s field of view. The three-axis-stabilized bus and preprogrammed magnetic-field-aligned pitch maneuver are designed to meet these requirements, while the residual pointing knowledge will be provided by the commercial spacecraft attitude solution.

The two MAG sensors deployed on a 60-cm boom (Figure 17c) are offset at an angle of 30° from nadir to avoid the fields of view of the eEPAA and FAI (Figures 17c,d). The eEPAA is mounted on the anti-ram face, giving it a 0°–180° field of view while avoiding the deployed solar panels. The anti-ram face does not include the spacecraft payload expander section used on the other three faces, allowing it to accommodate the eEPAA and MAG boom in the interstitial space between the spacecraft and dispenser (Figure 18). The FAI camera points to nadir. The FAI electronics have a thermal path to a spacecraft face-sheet, which is normally eclipsed by the deployed solar panels to create a radiator for the TEC and maintain the FAI at a calibrated temperature of ∼15 °C with modest power dissipation. The standard nanosatellite avionics include S-band uplink and X-band downlink. CICADA has four X-band contacts per day at 10 Mbps, each averaging 400 s, allowing it ∼1,400 MB of payload data downlinking per day. A spacecraft-provided data processing board interfaces with the instruments and acts as a CPU for instrument-specific data handling software.

3.2.1 Payload assembly integration and test

Most instruments complete standalone vibration testing to NASA’s General Environmental Verification Specification (Milne and Kaufman, 2003) levels and ambient pressure thermal cycling prior to delivery for suite integration at Iowa. A spacecraft simulator from the spacecraft provider allows interface testing, instrument control, and data handling software development. A purpose-built printed wiring assembly is used to implement the standard harness connectors for each instrument and merge them into two spacecraft-standard power and telemetry connectors. The FAI is the only instrument without a universal asynchronous receiver-transmitter interface and is thus integrated first to allow time to validate the LVDS CameraLink Base interface and image binning software. The other instruments are then incrementally electrically integrated into the flat-sat until a comprehensive performance test (CPT) can be implemented on the entire instrument suite. Selected electromagnetic interference/electromagnetic cleanliness tests are also performed in the flat-sat configuration to confirm self-compatibility. Figure 18 shows the stowed layout of the instrument suite within the 12U payload volume. A purpose-built aluminum structure is used to position the instruments and provide thermal paths to the spacecraft. The instruments are integrated into this structure and electrically connected to the adapter board prior to starting the environmental qualifications for the instrument suite.

The complete instrument suite undergoes an accelerated thermal vacuum campaign at Iowa (shorter dwells, looser plateaus); the suite is connected to the spacecraft simulator outside the TVAC chamber through a wiring bulkhead. A successful CPT during TVAC is the acceptance criterion for delivery to the spacecraft. Then, representatives from the instrument teams accompany the instrument suite to the spacecraft provider and support with integration, culminating in a successful CPT executed through the flight computer. The spacecraft provider then completes spacecraft assembly and their standard environmental test campaign. Lastly, the spacecraft is installed in the nanosatellite dispenser and transferred to the access-to-space provider, who completes integrated operations with the launch provider for launching and on-orbit deployment.

3.2.2 Access to space

Access to space is contracted to a commercial rideshare provider who supplies a 16U dispenser and conducts the integrated launch-site activities. One face of the 16U spacecraft is omitted to create a volume that accommodates the eEPAA sensor and MAG boom outside the spacecraft but within the dispenser. This arrangement gives the eEPAA an appropriate field of view in the upward and downward directions of the magnetic field with only minor impingements and without requiring a mechanical actuator to deploy the eEPAA from the spacecraft on orbit. Similarly, the MAG boom is stowed within the dispenser but has an unobstructed path for deployment away from the spacecraft. The spacecraft is loaded into the 16U dispenser at the spacecraft provider’s facility and shipped in a Pelican case to the launch site. The commercial rideshare provider completes joint launch-site operations with the launch provider to mechanically mount the dispenser to its spacecraft tombstone alongside electronically connecting and validating the dispenser actuation. On-orbit, the dispenser door is opened so that the captive springs in the dispenser can eject the spacecraft. Finally, the spacecraft avionics detects separation and power up, and the contracted mission operations team at the spacecraft provider achieves radio contact and begins commissioning.

3.2.3 On-orbit operational plan

CICADA’s operational plan is extremely simple: once a week, the Science Operations Center (SOC) at Iowa propagates the current orbital two-line elements forward by 14 d and creates a time-tagged list of all fully eclipsed region-of-interest crossings with durations exceeding 30 s. These data are uploaded to an Amazon Web Services (AWS) online storage location, where the spacecraft provider’s automation software parses the file, prompts review by an operator, and uplinks the resulting time-tagged commands during the next spacecraft contact. All instruments are active in the region of interest, and science data are accumulated in the data processing board provided on the spacecraft. The spacecraft uses an existing attitude mode to continuously align to an onboard static magnetic field model, maintaining pointing within the required ±2.5° of the local field. Except for the FAI, the data from all instruments are stored at full cadence for downlinking.

The FAI is disabled outside the region of interest, and its cooler maintains the temperature of the charge-coupled device. The software provided by the science team is implemented in the back orbit to bin the cached raw FAI data at 4:1 and queue them for downlinking. The back orbit data from the MAG, EFI, and LP are continuously decimated by the software in the data processing board for a low-cadence calibration product. The spacecraft provider has full autonomy during the back orbit and alternates between a sun-pointing interval for battery charging and a target-tracking interval for ground contact. The back orbit always contains the dayside orbit portion to provide reliable charging opportunities. S-band uplink and X-band downlink are used for ground contact. The downlinked science data, spacecraft housekeeping data, and attitude and orbit ephemerides are automatically uploaded to an AWS online storage location so that the SOC at Iowa can collect them and commence the processing chain.

3.3 Orbit options

The region of interest defined for CICADA is 60°–75° latitude (and the equivalent southern hemisphere range) from 06:00 to 18:00 local time. Figure 19 shows how this region of interest encompasses most of the nightside auroral activity. Both noon–midnight sun-synchronous and polar orbits cross the auroral arcs nearly orthogonally (north–south), so the local FAC can be inferred from the cross-track component, as described under SO3.

The most likely orbit for CICADA is the common noon–midnight sun-synchronous orbit that provides consistent region-of-interest crossings sampling a single local time. If a rideshare opportunity becomes available, the ideal choice would be a 0° polar orbit to sweep out the magnetic local times. In a polar orbit, the local time of the ascending node would require 12 months to rotate through all local times irrespective of the orbital altitudes from 400 to 600 km. However, the rising and falling legs will sample all local times in 6 months. CICADA can only capture auroral images when fully eclipsed, as sunlight will otherwise wash out the image. Consequently, a local time and an altitude-dependent number are unusable when the spacecraft is illuminated even partially. A sun-synchronous noon–midnight orbit provides consistent region-of-interest imaging, albeit at a single local time. A polar orbit cannot be used for imaging near dawn–dusk but would traverse all local times. Figure 20 shows the usable region-of-interest crossings per week at altitudes of 400/500/600 km in the polar and sun-synchronous orbits. CICADA captures at least 1490 region-of-interest crossings over a period of 6 months regardless of the initial local time of the orbit.

3.4 Summary and conclusions

The CICADA mission concept uses a nanosatellite platform and low-cost instrumentation based on previous suborbital sounding-rocket missions to probe the connections among auroral forms, precipitating electrons, and Alfvénic wave–particle interactions in the Earth’s magnetosphere. By addressing three interconnected SOs, namely, quantifying Alfvénic associations with dynamic discrete arcs (SO1), establishing causal links between Alfvén waves and electron precipitation (SO2), and mapping FACs in pulsating auroras (SO3), CICADA bridges the gaps in our understanding of MI coupling. The mission’s instrument suite, which includes a gradiometer MAG, deployable electric field booms, a Langmuir probe, an electron analyzer, and the FAI, provides all necessary in situ and imaging data from a single spacecraft to enable robust statistical analyses across varying geomagnetic conditions over a 6-month baseline duration.

CICADA’s innovations extend beyond science and demonstrate cost-effective nanosatellite technologies, such as compact deployable booms for electric field measurements and postprocessed wave–particle correlations. These advancements ensure that the key technologies are mature for technical readiness level 6, facilitating future missions to the auroral acceleration region (4,000–6,000 km) and broadening nanosatellite applications in heliophysics. The mission is also aligned with NASA’s Heliophysics Decadal Survey Goals, offering new constraints on plasma turbulence, energy dissipation, and auroral electrodynamics. CICADA represents a pivotal step toward quantifying the fundamental processes involved in space plasmas, with implications for plasma physics, heliophysics, and space weather forecasting. It exemplifies efficient high-impact science in an era of resource-constrained exploration by leveraging commercial rideshare access and streamlined operations.

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Footnotes

Edited by: Yongliang Zhang, Applied Physics Laboratory, Johns Hopkins University, United States

Reviewed by: Muhammad Ayyaz Ameen, Pakistan Space and Upper Atmosphere Research Commission, Pakistan

Ephrem Tesfaye Desta, Addis Ababa University, Ethiopia