Stratospheric Balloon Mission Research Articles

Globin: A spectropolarimetric inversion code for the coupled inference of atomic line parameters

Context. The reliability of physical parameters describing the solar atmosphere inferred from observed spectral line profiles depends on the accuracy of the involved atomic parameters. For many transitions, atomic data, such as the oscillator strength (log(gf)) and the central wavelength of the line, are poorly constrained or even unknown. Aims. We present and test a new inversion method that infers atomic line parameters and the height stratification of the atmospheric parameters from spatially resolved spectropolarimetric observations of the Sun. This method is implemented in the new inversion code globin. Methods. The new method employs a global minimization algorithm enabling the coupling of inversion parameters common to all pixels, such as the atomic parameters of the observed spectral lines. At the same time, it permits the optimum atmospheric parameters to be retrieved individually for each spatial pixel. The uniqueness of this method lies in its ability to retrieve reliable atomic parameters even for heavily blended spectral lines. We tested the method by applying it to a set of 18 blended spectral lines between 4015 Å and 4017 Å, synthesized from a 3D magnetohydrodynamic simulation containing a sunspot and the quiet Sun region around it. The results were then compared with a previously used inversion method where atomic parameters were determined for every pixel independently (pixel-by-pixel method). For the same spectral region, we also inferred the atomic parameters from the synthesized spatially averaged disc-centre spectrum of the quiet-sun. Results. The new method was able to retrieve the log(gf) values of all lines to an accuracy of 0.004 dex, while the pixel-by-pixel method retrieved the same parameter to an accuracy of only 0.025 dex. The largest differences between the two methods are evident for the heavily blended lines, with the former method performing better than the latter. In addition, the new method is also able to infer reliable atmospheric parameters in all the inverted pixels by successfully disentangling the degeneracies between the atomic and atmospheric parameters. Conclusions. The new method is well suited for the reliable determination of both atomic and atmospheric parameters and works well on all spectral lines, including those that are weak and/or severely blended. This is of high relevance, especially for the analysis of observations of spectral regions with a very high density of spectral lines. An example includes the future near-ultraviolet spectropolarimetric observations of the SUNRISE III stratospheric balloon mission.

On the use of cup anemometers as wind speed sensors in stratospheric balloon missions

Stratospheric balloon missions have emerged as a cost-effective alternative to space missions for scientific research and technology development. These missions enable the collection of critical data from the Earth’s upper atmosphere while reducing financial and logistical burdens associated with traditional space missions. One key challenge in these missions is the accurate measurement of the relative-to-the-gondola wind speed in the tropopause and the stratosphere. This paper explores the viability of using cup anemometers as wind speed sensors in stratospheric balloon missions, offering an easy-to-calibrate, low-cost, and accurate solution. The present paper provides a short overview of stratospheric balloon missions and their relevance in atmospheric research and outlines the challenges and limitations of existing wind speed sensing technologies. The cup anemometer is also described, detailing its working principle, advantages, and limitations, and propose a methodology for incorporating the instrument into stratospheric balloon missions. To validate the proposed methodology, a stratospheric balloon mission (the Tasec-Lab experiment, onboard a B2Space balloon launched in 2021), was equipped with a cup anemometer whose performance was analyzed. The results prove that cup anemometers can provide accurate and reliable relative wind speed measurements in the tropopause and the stratosphere. Furthermore, the low power consumption and the ease of development and calibration of cup anemometers make them an attractive option for stratospheric balloon missions.

Design and implementation of a real-time onboard system for a stratospheric balloon mission using commercial off-the-self components and a model-based approach

Stratospheric balloons have emerged as an affordable and flexible alternative to traditional spacecrafts as they are implemented using commercial off-the-shelf (COTS) equipment without following strict methodologies. HERCCULES is a stratospheric balloon mission that aims to characterize the convective heat and radiative environment in the stratosphere. The purpose of this article is to present the HERCCULES onboard software (OBSW) whose design and complexity is comparable to that of satellite systems, since it must control about sixty COTS equipment using a single Raspberry Pi 4B as onboard computer and ensure the real-time requirements. Compared to similar systems, novel contributions are presented as the OBSW is developed following model-based and component-based approaches using the TASTE toolchain from the European Space Agency (ESA) for automatic code generation. Besides, the OBSW is verified and validated following the ESA standards and the results obtained demonstrate the suitability and efficiency of the solution and the selected methodologies.

Study of secondary cosmic rays using small stratospheric balloon missions

Study of secondary cosmic rays using small stratospheric balloon missions

Risk Assessment and Experimental Light-Balloon Deployment of a Stratospheric Vertical VLF Transmitter.

This paper discusses the risks associated with an aerostat-supported stratospheric (unanchored) balloon mission equipped with a long vertical antenna and a very low frequency radio transmitter. The risks have been grouped into four main types and applicable mitigation methods have been presented to provide a sufficient level of safety and reliability to such a balloon mission. An experimental mission consistent with this analysis, based on the described theoretical VLF propagation approach, has been prepared and launched, and is operating at 14.2 kHz with a vertical antenna of a total length of 400 m and a total payload of max. 4 kg. The maximum altitude reached 29,164 m. The experiment's signal has been registered in numerous locations in Europe; the results are compared with numerical analysis employing a hypothesis of an apparent transmitting frequency decrease with the rise of the transmitter's altitude. The numerical analysis explains the behavior of the experimental signal and remains generally consistent with the hypothesis.

Hardware qualification for scientific ballooning missions

The European Stratospheric Balloon Observatory (ESBO) initiative aims at simplifying the access to stratospheric balloon missions. We plan to provide platforms and support with instrument design in order to support scientists. During the design process, the inevitable question of qualification for the harsh flight conditions arises. Unfortunately, there is no existing standard for qualification of stratospheric ballooning hardware. Thus, we developed a qualification procedure for use within ESBO and similar projects.In this paper, we present our analysis of the environmental conditions in the stratosphere. While conditions at typical balloon float altitudes are similar to the space environment, there are also some relevant differences. For example, the thermal environment is dominated by radiation and thermal conduction, but the remaining atmosphere still supports a certain amount of convection. The remaining atmospheric pressure in the stratosphere also leads to reduced arcing distances. Vibrational loads are far less than for space missions, but quasi-static or shock loads may occur. The criticality of radiation increases with mission duration.Based on the environmental conditions, we present the qualification procedures for ESBO, which are based on the European Cooperation for Space Standardization (ECSS) standards for space systems. Overtesting against too high requirements leads to overengineering, driving mission cost and mitigating the advantages of balloons over space missions. Therefore, we modified the ECSS standards to fit typical scientific ballooning missions over several days at altitudes up to 40 km. Furthermore, we analyzed design rules for space systems with regard to their relevance for scientific ballooning, including material and component selection. We present the experience from the hardware qualification process for the ESBO prototype STUDIO (Stratospheric UV Demonstrator of an Imaging Observatory). Even though boundary conditions are different for each individual mission, we aimed for a broader approach: We investigated more general requirements for scientific ballooning missions to support future flights.

Measuring Relative Wind Speeds in Stratospheric Balloons with Cup Anemometers: The TASEC-Lab Mission

This paper shows wind speed measurements from the TASEC-Lab experiment in a stratospheric balloon mission. The mission was launched in July 2021 from León (Spain) aerodrome. Measurements of horizontal wind speed in relation to the balloon gondola were successfully carried out with a cup anemometer. According to the available literature, this is the first time a cup anemometer has been used in a stratospheric balloon mission. The results indicate the need to consider the horizontal wind speed from the balloon ascent phase for thermal calculations of the mission.

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).

Experiential Systems Engineering Education Concept Using Stratospheric Balloon Missions

This paper proposes the concept of experiential systems engineering (ESE) as a hands-on education approach for teaching systems engineering (SE) tools and methods in postgraduate university courses, following the conceive, design, implement, and operate (CDIO) approach to modern engineering education. It describes ESE as implemented by the author and his research team in the Space Systems Engineering courses at Skoltech over the course of Fall 2014–Spring 2017. It describes the experience of student cohorts in applying SE to stratospheric balloon missions for education purposes, simulating real-life project experience including customer interface management, and operating projects designing and implementing an SE management plan. It describes the proposed approach and provides lessons learnt to generalize ESE to any specific engineering discipline of interest. A mapping between the learning objectives of ESE and the CDIO education framework is proposed. It extends the concept of hands-on SE education. It will be useful to educators interested in novel approaches to SE education and to experiment new ways to deliver a subject that is traditionally believed difficult to teach in university.

The short wavelength instrument for the polarization explorer balloon‐borne experiment: Polarization modulation issues

In this paper we investigate the impact of using a polarization modulator in The Short Wavelength Instrument for the Polarization Explorer (SWIPE) of the large scale polarization explorer (LSPE). The experiment is optimized to measure the linear polarization of the cosmic microwave background at large angular scales during a circumpolar long‐duration stratospheric balloon mission, and uses multimode bolometers cooled to .3 K. The 330 detectors cover three bands at 140, 220, and 240 GHz. Polarimetry is achieved by means of a large rotating half‐wave plate (HWP) and a single wire‐grid polarizer in front of the arrays. The polarization modulator is the first polarization‐active component of the optical chain, reducing significantly the effect of instrumental polarization. A trade‐off study comparing stepped versus spinning HWPs drives the choice towards the second. Modulating the cosmic microwave background polarization signal at four times the spin frequency moves it away from 1/f noise from the detectors and the residual atmosphere. The HWP is cooled to 1.6 K to reduce the background on the detectors. Furthermore, its polarized emission combined with the emission of the polarizer produces spurious signals modulated at 2f and 4f. The 4f component is synchronous with the signal of interest and has to characterized to be removed from cosmological data.

Selection of extreme environmental conditions, albedo coefficient and Earth infrared radiation, for polar summer Long Duration Balloon missions

The selection of the extreme thermal environmental conditions –albedo coefficient and Earth infrared radiation– for the thermal design of stratospheric balloon missions is usually based on the methodologies applied in space missions. However, the particularities of stratospheric balloon missions, such as the much higher residence time of the balloon payload over a determined area, make necessary an approach centered in the actual environment the balloon is going to find, in terms of geographic area and season of flight. In this sense, this work is focussed on stratospheric balloon missions circumnavigating the North Pole during the summer period. Pairs of albedo and Earth infrared radiation satellite data restricted to this area and season of interest have been treated statistically. Furthermore, the environmental conditions leading to the extreme temperatures of the payload depend in turn on the surface finish, and more particularly on the ratio between the solar absorptance and the infrared emissivity α/ε. A simple but representative thermal model of a balloon and its payload has been set up in order to identify the pairs of albedo coefficient and Earth infrared radiation leading to extreme temperatures for each value of α/ε.

Radiation damage of polyethylene exposed in the stratosphere at an altitude of 40 km

Low-density polyethylene (LDPE) films were exposed at an altitude of 40 km over a 3 day NASA stratospheric balloon mission from Alice Springs, Australia. The radiation damage, oxidation and nitration in the LDPE films exposed in stratosphere were measured using ESR, FTIR and XPS spectroscopy. The results were compared with those from samples stored on the ground and exposed in a laboratory plasma. The types of free radicals, unsaturated hydrocarbon groups, oxygen-containing and nitrogen-containing groups in LDPE film exposed in the stratosphere and at the Earth's surface are different. The radiation damage in films exposed in the stratosphere are observed in the entire film due to the penetration of high energy cosmic rays through their thickness, while the radiation damage in films exposed on the ground is caused by sunlight penetrating into only a thin surface layer. A similarly thin layer of the film is damaged by exposure to plasma due to the low energy of the plasma particles. The intensity of oxidation and nitration of LDPE films reflects the difference of atmospheric pressure on the ground and in the stratosphere. The high-density radiation damage of the LDPE films above the ozone layer in the stratosphere is caused by primary cosmic rays as well as collision induced cosmic ray air showers, and is consistent with the measured flux of cosmic radiation. The results show, that stratospheric flights can be used to simulate the effects of space environments during interplanet space flights for the purposes of investigating the degradation of polymer materials.

Terahertz Photometer to Observe Solar Flares in Continuum

Solar observations at sub-THz frequencies detected a new flare spectral component peaking in the THz range, simultaneously with the well known microwaves component, bringing challenging constraints for interpretation. Higher THz frequencies observations are needed to understand the nature of the mechanisms occurring in flares. A THz photometer system was developed to observe outside the terrestrial atmosphere on stratospheric balloons or satellites, or at exceptionally transparent ground stations. The telescope was designed to observe the whole solar disk detecting small relative changes in input temperature caused by flares at localized positions. A Golay cell detector is preceded by low-pass filters to suppress visible and near IR radiation, a band-pass filter, and a chopper. A prototype was assembled to demonstrate the new concept and the system performance. It can detect temperature variations smaller than 1 K for data sampled at a rate of 10/s, smoothed for intervals larger than 4 s. For a 76 mm aperture, this corresponds to small solar burst intensities at THz frequencies. A system with 3 and 7 THz photometers is being built for solar flare observations on board of stratospheric balloon missions.

IMaX: a polarimeter based on Liquid Crystal Variable Retarders for an aerospace mission

AbstractIMaX is the Imaging Magnetograph eXperiment, an instrument part of the payload of SUNRISE, a stratospheric balloon mission in Antarctica. It is also the precursor of the Visible Imaging Magnetograph of the future ESA Solar Orbiter mission. It is essentially a diffraction‐limited imager that carries out spectropolarimetric measurements of high resolution (bandwidth of < 100 mÅ at 525.02 nm), and relates the polarimetric properties of the incoming light through a telescope with magnetic fields in the Sun, via the Zeeman effect. At the core of the instrument there are the polarization modulation components, two Liquid Crystal Variable Retarders (LCVRs). A demodulation efficiency is defined and used as the figure of merit, and it serves to find the theoretical optimum states for the LCVRs as well as to judge the quality of the pre‐flight calibration of the system. This calibration and the method used to optimize the actual efficiency is explained. Also, the space qualification of the LCVRs is presented, where ellipsometry played a major role in studying the effects of radiation, vacuum and temperature in the operation of the LCVRs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A distributed model of a space heat pump under transient conditions

A prototype heat pump was designed and tested, as means of active thermal management for electronics packages to be used on stratospheric balloon missions. The evaporator worked as a cold plate to absorb heat dissipated by the electronics, while the condenser rejected heat primarily by radiation to the rarified environment. To predict the transient performance of the heat pump under varying environmental temperature and cooling load conditions, a dynamic model of the heat pump is created with a graphical user interface (GUI). The simulation of the evaporator and condenser are fully transient and the components are segmented, whereas the compressor and expansion device are lumped models and assumed to be at quasi-steady state. A detailed model for the mass and energy conservation in the two heat exchangers is presented. The spatial and temporal variation of temperature and mass flow rate in the heat exchangers are predicted. Several types of transient conditions such as step changes of the space temperature and cooling load, system start-up, shutdown, and cycling, are studied. The space temperature, cooling load, compressor power, mass flow rates of the compressor and expansion device, pressures and refrigerant charges of the condenser and evaporator, and temperature distribution in the heat exchangers are dynamically displayed on the GUI. The simulation results are compared with experimental data for step changes in the cooling load and show good agreement in terms of trends. Copyright © 2002 John Wiley & Sons, Ltd.