SAIL is actively involved with several sounding rocket missions. Sounding rockets are the only means of investigating the Earth’s mesosphere (60-90 km) and the lower thermosphere (90-250 km). Sounding rockets can also be used to investigate higher altitudes (250-1200 km) and are launched whenever there is an active phenomenon underway as observed by ground-based observations. In the United States, scientific sounding rockets missions are managed by the NASA Wallops Flight Facility, and in Germany, they are managed by the DLR MORABA. Two of SAIL’s recent sounding rocket projects were a NASA MTeX mission and a DLR WADIS mission.
Brief introductions and a few pictures for each of these missions are provided in the accordions below.
Solar eclipses present a truly unique opportunity to study the effects of a supersonic cooling shadow and its modulation of the structure and energetics of the ionosphere-thermosphere system. Atmosphere Perturbation around Eclipse Path (APEP) is a comprehensive sounding rocket campaign designed to study these eclipse dynamics. The mission name takes inspiration from the serpent deity Apep from ancient Egyptian mythology. Apep is the nemesis of the Sun deity Ra and is said to have pursued him and, every so often, nearly consumed him, resulting in an eclipse.
APEP is an eclipse rocket campaign that launched three rockets from White Sands Missile Range during the October 2023 annular eclipse and will launch three rockets from the Wallops Flight Facility during the April 2024 total eclipse. This campaign will be the first simultaneous multipoint spatio-temporal in-situ observations of electrodynamics and neutral dynamics associated with solar eclipses. For each eclipse, the first of the three instrumented rockets will be launched 35-45 minutes before peak local eclipse, the second at peak local eclipse, and the third 35-45 minutes after peak local eclipse. The launches will be supported by comprehensive ground-based observations through digisondes, meter wind radar, ISR, as well as high-altitude balloon launches to see meteorological forcing from below Observations will be used to constrain comprehensive modeling during data analysis.
Chimonas in 1970 postulated that an eclipse shadow can result in internal gravity waves which then show bow-wave patterns in Traveling Ionospheric Disturbances (TIDs) in the ionosphere. The eclipse-induced ionospheric irregularities have been a topic of interest since then, and the recent total solar eclipse of 2017 provided the community with an opportunity to obtain important ground- and space-based measurements to assess the impact of the eclipse, such as the generation of large scale TIDs published by Coster et al. 2017.
If one thinks of the ionosphere as a pond with gentle ripples, the eclipse is like a motorboat that suddenly rips through the water. This creates a wake immediately underneath and behind it, and the water level momentarily goes up as it rushes back in. This is visualized in a differential TEC map presented by Mrak et al. in 2018, which shows normal ‘ripples’ in dTEC existing before the 2017 eclipse and then the eclipse streaking across the continental USA.
In addition to the above studies, the temperature and density gradients resulting from eclipse can seed instabilities such as the Temperature Gradient Instability and Gradient Drift Instability. With the right conditions, these mechanisms can seed irregularities in scales of a few meters to 100s of meters that can cause scintillation of radio signals, which cannot be captured with large-scale simulations currently used by the community. Physical processes perturbed by eclipse extend well beyond the maximum period of totality into the penumbra [Goncharenko et al. 2018], appear across vast geographical expanses [Coster et al. 2017] and disrupt communication paths.
Given that solar eclipses of any type (total, annular, or partial) occur only about twice every year at some point over the Earth, opportunities to study them and their effects on the ionosphere thermosphere systems are limited due to limitations of comprehensively instrumented remote sensing sites along the path of the eclipse. Even rarer is the passage of an eclipse over/near a NASA sounding rocket launch site.
The passage in October 2023 of an annular eclipse almost overhead White Sands Missile Range, and the passage in April 2024 of a total solar eclipse in relative proximity of Wallops Island, presents a compelling opportunity to perform simultaneous multipoint in-situ measurements at extremely fine spatial scales supported by myriad ground-based remote sensing instrumentation. This should provide crucial insight in understanding and modeling the physical processes associated with eclipses that result in ionospheric and thermospheric disturbances. The next similar opportunity from the U.S. mainland is in 204
After the launch, the subpayloads get deployed at ~107 km at ~3 m/s ejection velocity. As all four move orthogonally away from the main payload, the payload flips, ejects the nosecone, deploys the booms and begins science measurements at 180 km upleg Altitude. The science measurements pause at 325 km altitude and the rocket flips to align into downleg RAM direction. The science measurements then continue until 70 km downleg, all the while the Subpayload continues moving away horizontally but in a parallel parabolic arc.
While the rocket measurements are going on, the ERAU team will release high-altitude balloons every 20 minutes starting two hours before peak eclipse (roughly 8:30 a.m. local time) and continuing until two hours after peak eclipse (12:30 p.m. local time). The ground station is able to track up to six balloons simultaneously, and the lifetime of each balloon is about two hours. The peak altitude achieved is about 28-30 km. This will give lower atmosphere winds and temperature. Co-investigator institution Air Force Research Lab will do continuous measurements of mesosphere winds (75-110 km) as well as ionosphere measurements using multiple ionosondes. These large-scale, ground-based measurements will be coupled with in-situ, small-scale measurements to feed into the modeling studies that are being led by CU Boulder (now JHU APL) and ERAU scientists. We will also be bringing in measurements from the larger science community as well as GPS TEC maps.
| Traceability Matrix | |||
|---|---|---|---|
| Science Questions | Measurement Requirements | Expected Instrucment Performance | Mission Functional Reg |
| Q1: Does the eclipse shadow directly seed discernible irregularities in the mid-latitude ionosphere? What are their length and time scales? Q2: What are the impacts of density, temperature and conductivity gradients in seeding small-scale (10s of meters to kilometers) ionospheric irregularities in the presence of solar eclipse? Q3: How do the different layers of the ionosphere behave differently in response to the overall cooling effect of the thermosphere? |
Magnetic Fields: ≤ 1 nT sensitivity ≤ 100 m spatial resolution In-situ Plasma Density: 1 m spatial resolution 1000 - 2x106 /cm range 100 /cm resolution Electron/lon Temperature: 300 - 3000K 100 K resolution E-fields: ≤ 0.1 mV/m resolution ≥ DC to 50 Hz bandwidth Neutral Density: 5 m resolution 108-1012 /cm3 range |
Magnetometer: < 0.1 nl sensitivity ≤ 1 m resolution Langmuir Probe Suite: ≤ 0.2 m resolution 1000 - 10' /cm range 50 /cm resolution Electron/lon Temperature: 300 - 3000K 100 K resolution Electric Field Probes: ≤ 0.1 mV/m resolution ≥ DC to 500 Hz bandwidth lonization gauge measurements down to 1e-7 torr with a <20% sensitivity in pressure variation. |
Three rockets launched in various phases of the eclipse. One before max obscuration, one at peak obscuration and one much later. Each instrumented rocket ejects up to four instrumented subpayloads to measure simultaneous plasma density variations. Recovery of instrumented payload in WSMR for relaunch at Wallops. |
The above table lists the three specific science questions that the mission is trying to address. In order to do so, we drive ourselves with some physical quantity measurement requirements and then select instruments that achieve those requirements for flight aboard the rockets. Furthermore, there are some mission requirements necessary to achieve the spatio-temporal variability.
Triple Rocket Launch During the 2023 Annular Eclipse
Watch all three sounding rockets from NASA’s APEP campaign launch in sequence during the annular eclipse at White Sands Missile Range. This edited footage captures the critical moments around liftoff as the mission collects data on how eclipses impact the upper atmosphere.
SpEED Demon was a NASA-funded sounding rocket technology demonstration risk-reduction mission that tested a comprehensive science instrumentation package with a sounding rocket launch on August 23, 2022, from Wallops Flight Facility in Virginia. The launch occurred at 9:16 p.m. local time.
SpEED Demon stands for Sporadic-E ElectroDynamics Demonstration mission. The exact same payload will fly on the NASA-funded SEED mission, with the scientific goal of studying low-latitude Sporadic-E layers.
The main payload consisted of a Sweeping Langmuir Probe for plasma density and electron temperature, a pair of Multi-Needle Langmuir Probes for 5KHz electron density, a Positive Ion Probe for relative ion density, ionization gauges and sensitive accelerometers for background neutral density, a suite of sensitive magnetometers, and a pair of electric field measurements. The main payload also ejected four sub-payloads, each carrying ion density measurement along with a sensitive magnetometer and an accelerometer capable of performing "falling sphere" analogous neutral density measurements. The launch was supported by ground-based observations from VIPIR Dynasonde MIT Millstone Haystack ISR.
Late August is the tail end of the Northern Hemisphere Sporadic-E (Es) Layer season, and SpEED Demon was launched into an Es layer as detected by VIPIR radar.
Most instruments were operated at a 5 KHz sampling rate, giving a better than 30 cm spatial resolution of most physical quantities: plasma and neutral density, magnetic and electric fields.
Versions of the mNLP, PIP and FPP instruments are also being built for the NASA ESCAPADE dual satellite mission to Mars. Thus, this mission will also increase the TRL of these instruments for interplanetary missions.
Results of the mission are being prepared for multiple journal manuscripts. First-cut results from various instruments were presented at the AGU Fall Meeting 2022 and CEDAR Workshop in Summer 2023. These are linked below:
- An overall payload overview with instrument performance characteristics as presented by Dr. Robert Clayton.
- Magnetic field measurements inside the Sporadic E layer by Dr. Joshua Milford.
- Detailed analysis and presentation of the simultaneous multi-point density measurements from ejected sub payloads by Dr. Henry Valentine.
- Neutral density measurements from falling cylinder accelerometer data by Dr. Nathan Graves.
“Sporadic-E (Es)” (90-125km) is a generic term used to describe thin (one to several km) ionization layers that are typically formed in the E region ionosphere. The density within the Es layers is several factors to a few orders of magnitude higher than the background ionosphere and can sometimes get higher than the F-region densities. One can think of these layers as "clouds of enhanced ionization." Similar to troposphere clouds, the Es clouds can be patchy puffs or a blanketing overcasting layer. These layers are generally believed to be a result of wind shears in the E-region ionosphere, but this mechanism is overly simplified and does not explain all the observed layer features. And despite decades of observations and modeling efforts of Es layers, there is a lack of complete understanding of Es layers and the role they play in E-F region coupling, especially at low latitudes. Degradation of RF communications and operational anomalies/failures during ionospheric disturbances are a crucial space weather influence on modern life. Es layers are the sole ubiquitous space weather source in the ionosphere that produce scintillations during nighttime and daytime, affecting operational RF transmissions such as HF, VHF and UHF communication links, as well as over-the-horizon radar and communications.
The NASA SEED mission aims to do comprehensive measurements of the electrodynamics associated with Es layers observed at the low latitude location of Kwajalein Atoll in Marshall Islands. In particular, SEED aims to investigate density-temperature anti-correlations as shown below and reported by Barjatya et al [2013]. The figure below shows a unique double Es layer situation wherein the electron temperature heats up above and below an Es layer but not within the layer. The bottom Es layer (107 km) is clearly located at a wind shear, but the top layer seems to be associated with electric fields. We believe this is a result of field-aligned currents, and SEED aims to investigate this hypothesis.
SEED is a comprehensive experiment to address a series of specific but interlinked science questions related to the Es layer phenomena, especially high altitude (>100 km) Es layers, at a low-latitude location (Kwajalein) during solar-min. Progress on these three questions will also contribute to the broader science goal of understanding the role of Es layers in ionosphere coupling:
- Are low-latitude/equatorial Es layers associated with field-aligned currents (FAC) of a magnitude of 1 to 2 uA/m2 in the presence of a nighttime F region dynamo?
- How do electric fields and winds modulate temperatures and conductivities in the E region via field-aligned currents?
- How consistent are the in-situ measurements across two distinct night observations?
The SEED mission consists of two comprehensively instrumented rockets, which will be launched on two separate nights, from Kwajalein Atoll in the Marshall Islands, during the summer of 2025. The figure below presents a conceptual diagram of the payload with a conceptual layout for the proposed instrumentation (Note: TMA payload that will separate along with rocket motor is not shown). Under the nose cone, there is one fixed boom for a Sweeping Langmuir Probe (SLP) and four folding deployed booms that will have two sets of multi-needle fixed bias DC Langmuir Probes (mNLP), a Positive Ion Probe (PIP) and a pair of magnetometers from PNI Sensors Corp. Under the aft skirt will be four telescoping stacer booms for the floating potential measurements (FPP), as well as a Billingsley Ultra Miniature Flight Magnetometer at the end of a fixed boom. The two sets of 180 degrees opposite FPP booms then consist of a typical double probe electric field measurement, while each of the four also gives payload-charging measurements.
The mission started in Summer 2019. It has been delayed due to a variety of scheduling issues, including the COVID-19 pandemic, and is currently slated to launch in Summer 2025. The payload demonstration mission, SpEED Demon, was launched in August 2022.
The NASA MTeX mission addresses the fundamental question of the contribution of wave-generated turbulence to energetics and mixing in the mesosphere and lower thermosphere (MLT) in the presence of persistent regions of stability and instability. The MTeX mission achieves the above objectives through two similar instrumented rocket campaigns aided by comprehensive, ground-based measurements from the Poker Flat Rocket Range.
The rockets were launched with a time gap of 35 minutes into a persistent mesosphere inversion layer on the morning of Jan. 26, 2015. Each instrumented rocket consists of a multi-surface, fixed-bias DC Langmuir probe (mDCP), Swept Impedance Probe (SIP), Sweeping Langmuir Probe (SLP) and the CONE (Combined measurement of Neutrals and Electrons) sensor. The boom-deployed instruments were contributed by SAIL, whereas the CONE sensor and electronics were from the University of Alaska Fairbanks and the Institute of Atmospheric Physics (Germany).
A good overview of the project can be found in an SPIE paper.
All instruments went through integration and testing at the NASA Wallops Flight Facility in Fall 2014. The integration was supported by Adam Blake, who did his Master of Science in Engineering Physics research work on the mission, and Zachary Laurencio, an undergraduate Engineering Physics student. The booms were designed and built by Finn Carlsvi and Ben Wallace, who were both undergraduate students in the Engineering Physics program. The boom deployment was spin-tested in SAIL at 5Hz on a student-designed and -built spin table. They were also spin-tested during integration and testing at NASA WFF.
The overall contributions from SAIL-built instruments were plasma density measurements in the MLT region for the two flights. The instruments provided high-cadence plasma density measurements that correlated well amongst different instrument types as well as ground-based radar measurements. This is shown in the figure below.
The German WADIS mission addresses the fundamental question of the energy budget of the MLT by trying to quantify the effect of selected wave events on turbulent heat production and diffusion, subsequent downward transport of atomic oxygen, and corresponding heat production by radiation and chemical reactions.
The WADIS mission achieves the above objectives through two similarly instrumented rocket campaigns aided by comprehensive ground-based measurements from the Andoya Rocket Range; one launch in polar summer and one in polar winter. The WADIS-1 launch was on June 27, 2013, and WADIS-2 launched in March 2015.
Each instrumented rocket consists of:
- Faraday rotation experiment (WAVE) and ion Langmuir probe (PIP) - Graz University of Technology, Austria
- IAP particle detector (IAP-PD) and Combined measurement of Neutrals and Electrons sensor (CONE) - Leibniz Institute of Atmospheric Physics
- Multi-surface, fixed-bias DC Langmuir probe (mDCP) - Embry‑Riddle Aeronautical University
The mDCP was designed by undergraduate students and engineers working at Embry‑Riddle under the direction of Dr. Barjatya, who was a Co-Investigator on the WADIS mission.
The first results of the WADIS-1 rocket have been published in Annales Geophysicae.
The mDCP probe is a unique implementation of Langmuir probe technique that measures the difference in triboelectric current collection by three different metallic surfaces. Charging of metallic surfaces by charge transfer from dust particles, due to differences in work functions or due to frictional contact, is known as triboelectric charging. If two surfaces merely come in contact with each other and then separate, the surface with a lower work function loses an electron to the surface with a higher work function.
This triboelectric current to a surface moving in dusty plasma is in addition to any thermal plasma current. Barjatya and Swenson [2006] have already shown the importance for considering the effects of triboelectrification on the interpretation of Langmuir-type probe datasets in the presence of dusty plasma. The WADIS mDCP probe is shown in the picture below.
