Stratospheric Balloon Research Articles

A Low-Cost Attitude Determination System using Multiple Sensors for High-Altitude Balloon Flights

This paper discusses the calibration and implementation of a low-cost attitude determi- nation system for high-altitude balloon flights using multiple sensors. The attitude determination system is comprised of a 3-axis accelerometer and a sun sensor. The accelerometer is utilized to measure the gravitational acceleration vector of the payload in the payload's body frame. The measured acceleration vector is based upon the accelerometer's bias and sensitivity which can be found through calibration under zero motion conditions. The sun sensor is comprised of many solar cells at various angles. These are utilized to obtain an accurate sunlight directional vector of the payload in the payload's body frame from an over-determined system of measurement equations. The development of these equations is discussed. Both the gravitational acceleration vector and the sunlight directional vector can also be measured in an inertial frame. It is assumed that these measurements are known a-priori. This provides enough information to solve for an attitude at each sample instance, utilizing two independent vector measurements (i.e., the sunlight and acceleration vectors). The attitude determination system utilizes Markley's solution to Wahba's problem. A 3-axis rate gyroscope is also utilized to gather angular velocity information of the payload in the payload's body frame and was used to compare against angular velocity derived from the estimated attitude to validate the accuracy of the attitude determination system. The measured angular velocity vector is based upon the rate gyroscope's bias and sensitivity which can be found through calibration under zero motion conditions.

Progressing Science, Technology, Engineering, and Math (STEM) Education in North Dakota with Near-Space Ballooning

The United States must provide quality science, technology, engineering, and math (STEM) education in order to maintain a leading role in the global economy. Numerous initiatives have been established across the United States that promote and encourage STEM education within the middle school curriculum. This study integrated a three-week long Near Space Balloon project into six eighth-grade Earth Science classes from Valley Middle School in Grand Forks, North Dakota. It was hypothesized that after the students designed, constructed, launched, and analyzed their payload experiments, they would have an increased affinity for high school science and math classes. A pre- and post-survey was distributed to the students (n=124), before and after the project, to analyze how effective this engineering and space mission was. The surveys were statistically analyzed, comparing means by the Student’s t-Test, specifically the Welch-Satterthwaite test. Female students displayed a 57.1% increase in math and a 63.6% increase in science; male students displayed a 46.6% increase in science and 0% increase in math. Most Likert-scale survey questions experienced no statistically significant change, supporting the null hypothesis. The only survey question that supported the hypothesis was, “I Think Engineers Work Alone,” which experienced a 0.24% increase in student understanding. The results suggest that integrating a three-week long Near Space Balloon project into middle school curricula will not directly influence the students’ excitement to pursue STEM subjects and careers. An extensive, yearlong ballooning mission is recommended so that it can be integrated with multiple core subjects. Using such an innovative pedagogy method as with this balloon launch will help students master the scientific process and experience real team collaboration, as they did with this successful mission.

Station-keeping for high-altitude balloon with reinforcement learning

The operating altitudes of the stratospheric balloons can reach near-space altitudes of more than 20 km, where the appearance of the quasi-zero wind layer follows the seasonal rule. As unmanned aerial vehicles with application potential, the effective flight control of balloon position is crucial. This research develops a station-keeping control approach based on reinforcement learning, and the control strategy also considers the characteristics of the local wind field. Firstly, an atmospheric environment model with an uncertain wind field is established according to the analysis of the historical wind data. The model serves as a training environment for the balloon station-keeping strategy training. Secondly, the thermal model, dynamic model, and altitude control model are introduced, and an environment based on historical real wind data is developed. Thirdly, the dueling double Q-learning deep network with prioritized experience replay method is applied to the station keeping of high-altitude balloons. The Priority Experience Replay based on High-Value Samples (HVS-PER) is developed to improve the stability of strategy training. Finally, the performance of the optimal network is evaluated by the total reward, horizontal displacement, and effective working time under the uncertain wind environment. The strategy analysis also has reference to exploiting appropriate initial positions and capturing the opportunity of releasing a balloon. This work confirms that the control strategy is viable in complex and variable wind field environments and is capable of long-duration flights.

Extended-range Variable Altitude Balloons for Venus atmospheric missions

In-situ exploration of Venus is challenging due to its severe environment, which is benign (∼25 °C and 1 bar) at an altitude of 55 km, but rapidly becomes hostile at lower altitudes. The temperature increases to ∼465 °C, and pressure reaches 90 bars at the surface. These conditions have limited in-situ missions to high altitude balloons at 55 km that survived only 48 h. High-altitude balloon missions are stymied by the opaqueness of the Venusian clouds and constant altitude. Long-duration, extended range variable-altitude balloons covering below the clouds could enhance the science capabilities of the missions by measuring chemical species, isotopes and atmospheric flow patterns in and underneath the clouds. A new energy storage system tolerant to the high temperatures at low altitudes is needed to support such a balloon. A novel variable altitude balloon architecture with an extended range of 55–20 km (VAB-X) was developed under the NASA Innovative and Advanced Concepts (NIAC) program and is described here. The architecture comprises a high-temperature tolerant balloon and photovoltaic array for providing spacecraft power, a reversible solid oxide fuel (SOFC) for low-altitude power and fuel regeneration, and reversible metal hydride (MH) for hydrogen storage. Hydrogen is used for the buoyancy and altitude control of the zero-pressure balloon and as fuel for SOFC. Water brought from Earth can replenish the hydrogen lost to leaks during the mission. Preliminary analyses reveal the efficacy of the architecture for long-term Venus exploration over 55-20 km altitude, with a high proportion (∼20%) of the total suspended mass (>20 kg) available for science payload.

Infrasound direction of arrival determination using a balloon-borne aeroseismometer.

Free-floating balloons are an emerging platform for infrasound recording, but they cannot host arrays sufficiently wide for multi-sensor acoustic direction finding techniques. Because infrasound waves are longitudinal, the balloon motion in response to acoustic loading can be used to determine the signal azimuth. This technique, called "aeroseismometry," permits sparse balloon-borne networks to geolocate acoustic sources. This is demonstrated by using an aeroseismometer on a stratospheric balloon to measure the direction of arrival of acoustic waves from successive ground chemical explosions. A geolocation algorithm adapted from hydroacoustics is then used to calculate the location of the explosions.

Dynamic coverage performance of wind-assisted balloons mesh based on Voronoi partition and energy constraint

Efficiently navigating a fleet of several thousand high-altitude balloons to provide communication network and information system to the entire Earth is a promising technology. Here we proposed the use of balloons with altitude control system to coverage the entire Earth by exploiting the natural time-varying wind field. The energy constraints are deduced based on the energy collecting-consuming model and the energy management strategy of the wind-assisted balloon. The Voronoi partition is introduced to optimize the configuration. Then a dynamic coverage algorithm for multi-balloons system is developed. Three schemes of 1500 balloons in two launch sites are simulated to show the effectiveness of the algorithm. The results demonstrate that Voronoi partition with energy constraints is an effective solution to spread the wind-assisted balloons out over the entire Earth within a short time and then maintain the optimal dynamic coverage configuration for quite a long time. This can serve as a guideline for the design and flight test of the serviceable wind-assisted balloons coverage mesh.

TASEC-Lab: A COTS-based CubeSat-like university experiment for characterizing the convective heat transfer in stratospheric balloon missions

The Thermal Analysis Support and Environment Characterization Laboratory (TASEC-Lab) is an experiment designed, integrated, and tested in the Universidad Politécnica de Madrid by bachelor's, master's and doctoral students. The aim of this project is to study the convection heat transfer, the thermal environment and the balloon dynamics during the ascent and float phases of a stratospheric balloon launched from the León (Spain) airfield on 16th, July 2021. TASEC-Lab has been designed following the CubeSat philosophy using commercial off-the-shelf (COTS) components. It consists of an aluminium structure of 130 × 130 × 330 mm3 with three compartments where the Electrical Power Subsystem, the Electronics, and the Heat Transfer Laboratory, are located. In addition, it carries a cup anemometer to be tested at the low-pressure conditions at high altitude to provide the relative speed of the balloon-gondola system in order to characterize the dynamics and the forced convection heat transfer. In this paper, the TASEC-Lab design is detailed as well as the different development phases considered in a university environment where all tasks were carried out by students, with the technical support of the research staff of the Instituto Universitario de Microgravedad “Ignacio da Riva” (IDR) and the group of Sistemas de Tiempo Real y Arquitectura de Servicios Telemáticos (STRAST).

Sonic anemometry on a high altitude balloon

Recent results demonstrate the promise of sonic anemometry for accurate, three dimensional, high update relative wind measurements in high altitude (stratospheric) balloons and for planetary science missions on Mars, Venus, and other environments [Banfield, JASA (2016); White, ASA (2020); White, AIAA (2020)]. The Tufts sonic anemometer, operating at 40kHz with six commercial piezoelectric transducers and custom electronics and frame, flew out of Fort Sumner, New Mexico on August 30 2021, reaching a height of 106°000 feet at float. The entire duration of the flight was 4 h and 42 min, with 2 h at float. The three axis sonic anemometry system collected sound speed and three dimensional relative wind velocity in two modes, at 3.4 Samples/sec or 1.5 Samples/sec. Results reported include comparison to balloon inertial and GPS motion to attempt to establish accuracy. Analysis is ongoing. [Work supported by NASA-NNX16AJ24G and NASA-80NSSC20M0007. Thanks to Chris Yoder and NASA Wallops Balloon Programs Office for technical support.]

High-Altitude Astrophotography and Investigating the Ionosphere: 2020 WSGC ELIJAH High-Altitude Balloon Payload

The objective of the 2020 WSGC Elijah High-Altitude Balloon Payload Team was to design a payload intended to collect data during the total solar eclipse taking place in April 2024. The COVID-19 pandemic posed unique challenges to the research team, primarily restricting their correspondence to remote meetings and preventing them from fabricating a payload to launch for flight testing. Ground-based experimentation was conducted to analyze the viability of each of the payload modules to be constructed and launched in a future research term. Two of the four designed experiments are elaborated on in this document: an astrophotography and luminance tracking system to image celestial objects and determine the visibility of deep-space objects, and a surveillance system to identify and measure variation in magnetic fields and solar radiation in the ionosphere.

2021 Elijah High-Altitude Balloon Payload

The 2021 WSGC Elijah High-Altitude Balloon Payload Team focused their projects on the upcoming 2024 solar eclipse. These included solar sensing, solar imaging, and the study of cosmic radiation. The solar sensing project involved collecting flight data such as altitude, temperature, and pressure. In addition to this data, quantitative UVA, UVB, light intensity, and solar energy values using various sensors and solar panels. Solar imaging utilized an action camera with solar, IR, and IR cut-off filters in conjunction with a 360-degree camera that captured the entire payload’s flight. The radiation shielding project focused on studying the effectiveness of low-density polyethylene as a radiation shielding material by comparing observations collected by shielded and unshielded Geiger counters. To observe radiation originating from nearby star systems, a particle detector consisting of a scintillator coupled to a silicon photomultiplier was constructed.

Increased utilization of real wind fields to improve station-keeping performance of stratospheric balloon

Stratospheric balloons are demonstrated overwhelming superiority in many aspects such as remote sensing, earth observation, meteorological service, and Internet connection. Stable connection with ground stations or signal receivers is important, and therefore, a balloon needs to remain located in a particular region. A time-varying range of achievable altitude algorithm is proposed in this paper to improve the flight performance of super-pressure balloon. The control principle, wind fields, and thermal models are established. The extended range of accessible altitude using this method is validated. Station-keeping performance of the balloon using this method is simulated and compared under three typical wind fields and 366-day real wind conditions at multiple locations between 48°N and 48°S. The results show the proposed method is efficient to increase the proportion of time floating within the desired region. Moreover, the method functions to decrease the maximum distance from the center point. Comparative analysis indicates the balloon with this method can take more advantage of local wind fields with a broader range of altitudes. The work also offers an effective solution on selections of districts and dates with appropriate wind fields to conduct long endurance projects and improve the station-keeping performance of balloons.

Active Tissue Equivalent Dosimeter: A Tissue Equivalent Proportional Counter flown onboard the International Space Station

The Active Tissue Equivalent Dosimeter (ATED) is a low-cost, easy-to-use and compact tissue equivalent proportional counter designed for use aboard spacecraft, satellites, aircraft, unmanned aerial vehicles and high-altitude balloons. ATED was rigorously tested at particle accelerator facilities utilizing heavy ions of charge and energy similar to Galactic Cosmic Rays (GCRs). Upon completion of the ground-based testing and calibration, the ATED was operated aboard the International Space Station (ISS) during July–August of 2018. ATED measurements from the ISS were then analyzed in terms of time, latitude, longitude, and altitude in order to correlate with the radiation fields in the ISS orbit. When ATED measurements were correlated with orbital position, elevated absorbed dose rates due to the South Atlantic Anomaly (SAA) were clearly evident. ATED measurements were also separated based on their orbital location into three different regions. The results from the July–August 2018 flight show that ATED functioned as designed while onboard the ISS. The hypothesis that lineal energy and linear energy transfer can be used interchangeably with measurements by a TEPC in Low Earth Orbit (LEO) was tested by ATED measurements. Lastly, a direct comparison was made between linear energy transfer (LET) converted from lineal energy spectra from a spherical TEPC in LEO and model-calculated LET values. Such a comparison is highly challenging with the TEPCs with cylindrical geometry previously used in space.

Reducing Spin on a High Altitude Balloon

The goal of this experiment was to reduce spin on an unmanned balloon as the altitude increases. This problem had been discovered after the initial flight, where the rotation of the Go-Pro camera was nearly sickening. After more research, it was found that every flight had the same lack of stability and high levels of rotation. The goal was then decided to try and reduce the spin of the payload so that stable pictures and video could be achieved. If there was a stable video going the whole way up, then the goal was considered complete, however, a gyroscope was included in each flight to find the reduction of spin in the payload.

Robust integrated control/structure co-design for stratospheric balloons

Stratospheric balloons offer cost-effective platforms for optical payloads in the context of astronomy missions. During the 2018 flight of the Faint Intergalactic medium Redshifted Emission Balloon (FIREBall) experiment, the moon light was scattered from the surface of the balloon and re-directed into the telescope which resulted in degraded optical performance. To reduce this parasite effect, it is sought to increase the length of the fight train. However, this change in the mechanical design significantly modifies the dynamics of the system and the pointing performance must not be altered. In this purpose, a robust integrated control/structure co-design method is proposed. After deriving a Linear Fractional Transformation (LFT) model of the system, the co-design is tackled as a multi-objective, structured, robust H2/H∞ problem that is solved with a non-smooth optimization algorithm to maximize the train's length under constraints of pointing performance. By optimizing in a single iteration the controllers along with the structural parameter with regard to the worst-case configurations of the uncertain parameters, time-consuming procedures requiring not only to iterate between control and mechanical design, but also to analyze the robustness based on Monte-Carlo simulations, are avoided.

Commercial GNSS Radio Occultation on Aerial Platforms With Off-The-Shelf Receivers

<h3>Abstract</h3> In recent decades, GNSS radio occultation (RO) soundings have proven to be an invaluable input to global weather forecasting. The success of government programs such as COSMIC is now complemented by commercial low-cost cubesats. The result is access to more than 10,000 soundings per day. We examine aerial platforms for commercial GNSS-RO, specifically high-altitude balloons and commercial aviation. Meteorological balloons (radiosondes) are deployed daily in over 900 locations globally. Adding GNSS-RO capability to radiosondes would expand capability and enable local area monitoring. Commercial aviation offers scale with more than 100,000 flights daily. A barrier to entry for the inclusion of GNSS-RO sensors is cost and complexity, as GNSS-RO traditionally requires highly specialized equipment. This paper describes a low-cost and scalable approach to aerial GNSS-RO based on commercial-off-the-shelf (COTS) GNSS receivers. We present hardware prototypes and data processing techniques that demonstrate technical feasibility through the results from several flight testing campaigns.

Development of a Balloon-Borne Acoustic Anemometer to Measure Winds for SENSOR Campaign

The Stratospheric Environmental respoNses to Solar stORms (SENSOR) campaign investigates the influence of solar storms on the stratosphere. This campaign employs a long-duration zero-pressure balloon as a platform to carry multiple types of payloads during a series of flight experiments in the mid-latitude stratosphere from 2019 to 2022. This article describes the development and testing of an acoustic anemometer for obtaining in situ wind measurements along the balloon trajectory. The anemometer is also equipped with temperature, pressure, and humidity sensors from a Temperature-Pressure-Humidity measurement module, inherited from a radiosonde developed for sounding balloons. The acoustic anemometer and other sensors were used in a flight experiment of the SENSOR campaign that took place in the Da chaidan District (95.37&#x00B0;E, 37.74&#x00B0;N) on 4 September 2019. Three-dimensional wind speed observations, which were obtained during level flight at an altitude of around 25 km, are presented. A preliminary analysis of the measurements yielded by the anemometer are also discussed. To our knowledge, this is the first time that wind measurements were obtained by an acoustic anemometer during level flight of the high-altitude balloon and were used to analyze Lagrangian spectrum in the inertial subrange over the Tibetan Plateau. In addition to wind speed measurements, temperature, pressure, and relative humidity measurements during ascent are compared to observations from a nearby radiosonde launched four hours earlier, and the results show very good agreement.

Orbit Simulator for Satellite and Near-Space Platforms Supporting Observing System Simulation Experiments

Abstract Developed at the National Oceanic and Atmospheric Administration (NOAA) and the Joint Center for Satellite Data Assimilation (JCSDA), the Community Global Observing System Simulation Experiment (OSSE) Package (CGOP) provides a vehicle to quantitatively evaluate the impacts of emerging environmental observing systems or emerging in situ or remote sensing instruments on NOAA numerical weather prediction (NWP) forecast skill. The typical first step for the OSSE is to simulate observations from the so-called nature run. Therefore, the observation spatial, temporal, and view geometry are needed to extract the atmospheric and surface variables from the nature run, which are then input to the observation forward operator (e.g., radiative transfer models) to simulate the new observations. This is a challenge for newly proposed systems for which instruments are not yet built or platforms are not yet deployed. To address this need, this study introduces an orbit simulator to compute these parameters based on the specific hosting platform and onboard instrument characteristics, which has been recently developed by the NOAA Center for Satellite Applications and Research (STAR) and added to the GCOP framework. In addition to simulating existing polar-orbiting and geostationary orbits, it is also applicable to emerging near-space platforms (e.g., stratospheric balloons), cube satellite constellations, and Tundra orbits. The observation geometry simulator includes not only passive microwave and infrared sounders but also global navigation satellite system/radio occultation (GNSS/RO) instruments. For passive atmospheric sounders, it calculates the geometric parameters of proposed instruments on different platforms, such as time varying location (latitude and longitude), scan geometry (satellite zenith and azimuth angles), and ground instantaneous field of view (GIFOV) parameters for either cross-track or conical scanning mechanisms. For RO observations, it determines the geometry of the transmitters and receivers either on satellites or stratospheric balloons and computes their slant paths. The simulator has been successfully applied for recent OSSE studies (e.g., evaluating the impacts of future geostationary hyperspectral infrared sounders and RO observations from stratospheric balloons). Significance Statement An orbit simulator for satellite and near-space platforms for supporting observing system simulation experiments (OSSE) is developed in this study. It can compute spatial, temporal, and view geometry parameters of the new observations based on the specific hosting platform and onboard instrument characteristics. These parameters are important for the OSSE to extract atmospheric profiles and surface properties from nature run data and simulate new observations. In addition to simulating existing polar-orbiting and geostationary orbits, it is applicable to emerging near-space platforms (e.g., stratospheric balloons), cube satellite constellations, and Tundra orbits. The observation geometry simulator includes not only passive microwave and infrared sounders but also radio occultation instruments.

Airborne Infrasound Makes a Splash

AbstractNatural and anthropogenic events may create low frequency sound waves, or infrasound, that can travel for vast distances in planetary atmospheres. They permit the remote monitoring of geophysical activity over local to global scales. Most studies have utilized ground‐based recorders, but it is possible to deploy acoustic sensors to altitudes of over 50 km. Such elevated platforms can capture sounds that their surface analogs cannot access. High altitude balloons and low altitude aerostats are filling this observation gap, but key environments remain out of reach of both of these. Recent work by den Ouden, Smets et al. (2021) addressed this with a new instrumentation platform—a large seabird flying just above the ocean's surface. Their work demonstrates that, infrasound sensing using heavier‐than‐air platforms in windy environments is possible, which has implications both terrestrially (e.g., extending sensor networks over the oceans) and extraterrestrially (proposed or planned missions to Venus and Titan).

Stratospheric Balloons Listen In on Ground Activity

Solar-powered hot-air balloons, floating 2.5 times as high as Mount Everest, detected a buried explosion more clearly than ground-based sensors did.

Flight test of an autonomous payload for measuring sky brightness and ground light pollution using a stratospheric sounding balloon

Light pollution is recognized as an increasingly important issue not only for astronomical observations but also for the preservation of ecosystem and the quality of human life. Emission from ground sources is currently mapped using satellite images aided by local ground observations but information has limited resolution in space and time; especially now that blue “cold” LEDs, which are poorly detected from space, are being widely used for illumination, data need to be integrated with measurement from autonomous systems flying at lower altitude.MINLU (“Misurazione dell’ INquinamento LUminoso”) autonomous payload was designed and tested to provide complete and detailed aerial observations of all light pollution sources and monitor sky brightness with the capability to be integrated on stratospheric balloons, tethered balloons or drones. The payload's architecture includes three downward looking cameras with dedicated filters and two commercial Sky Quality Meter (SQM-LE) units, one pointing in horizontal direction and the other monitoring the zenith sky. The system can achieve a ground sample distance of 3 cm when integrated on drones flying at 200 m altitude, going up to 8 m at altitudes above 30 km in the use with balloons; this considerably improves the information provided by satellite images showing a ground resolution around 800 m.The payload was successfully launched with a sounding balloon from Tuscany on July 8th, 2021 during the astronomical night window, achieving the first continuous observation of sky brightness magnitude in Earth atmosphere from ground to stratospheric altitudes. In parallel, images of on-board cameras have been used to quantify ground emission in terms of luminous intensity and power density and allowed to track sources causing the artificial luminance of the sky.