Instituto Nacional De Tecnica Aeroespacial Research Articles

Calibration OGSEs for multichannel radiometers for Mars atmosphere studies

This work describes several Optical Ground Support Equipment (OGSEs) developed by INTA (Spanish Institute of Aerospace Technology—Instituto Nacional de Tecnica Aeroespacial) for the calibration and characterization of their self-manufactured multichannel radiometers (solar irradiance sensors—SIS) developed for working on the surface of Mars and studying the atmosphere of that planet. Nowadays, INTA is developing two SIS for the ESA ExoMars 2020 and for the JPL/NASA Mars 2020 missions. These calibration OGSEs have been improved since the first model in 2011 developed for Mars MetNet Precursor mission. This work describes the currently used OGSE. Calibration tests provide an objective evidence of the SIS performance, allowing the conversion of the electrical sensor output into accurate physical measurements (irradiance) with uncertainty bounds. Calibration results of the SIS on board of the Dust characterisation, Risk assessment, and Environment Analyzer on the Martian Surface (DREAMS) on board the ExoMars 2016 Schiaparelli module (EDM—entry and descent module) are also presented, as well as their error propagation. Theoretical precision and accuracy of the instrument are determined by these results. Two types of OGSE are used as a function of the pursued aim: calibration OGSEs and Optical Fast Verification (OFV) GSE. Calibration OGSEs consist of three setups which characterize with the highest possible accuracy, the responsivity, the angular response and the thermal behavior; OFV OGSE verify that the performance of the sensor is close to nominal after every environmental and qualification test. Results show that the accuracy of the calibrated sensors is a function of the accuracy of the optical detectors and of the light conditions. For normal direct incidence and diffuse light, the accuracy is in the same order of uncertainty as that of the reference cell used for fixing the irradiance, which is about 1%.

OWLS as platform technology in OPTOS satellite

The aim of this work is to show the Optical Wireless Link to intraSpacecraft Communications (OWLS) technology as a platform technology for space missions, and more specifically its use within the On-Board Communication system of OPTOS satellite. OWLS technology was proposed by Instituto Nacional de Tecnica Aeroespacial (INTA) at the end of the 1990s and developed along 10 years through a number of ground demonstrations, technological developments and in-orbit experiments. Its main benefits are: mass reduction, flexibility, and simplification of the Assembly, Integration and Tests phases. The final step was to go from an experimental technology to a platform one. This step was carried out in the OPTOS satellite, which makes use of optical wireless links in a distributed network based on an OLWS implementation of the CAN bus. OPTOS is the first fully wireless satellite. It is based on the triple configuration (3U) of the popular Cubesat standard, and was completely built at INTA. It was conceived to procure a fast development, low cost, and yet reliable platform to the Spanish scientific community, acting as a test bed for space born science and technology. OPTOS presents a distributed OBDH architecture in which all satellite’s subsystems and payloads incorporate a small Distributed On-Board Computer (OBC) Terminal (DOT). All DOTs (7 in total) communicate between them by means of the OWLS-CAN that enables full data sharing capabilities. This collaboration allows them to perform all tasks that would normally be carried out by a centralized On-Board Computer.

Errata: Mapping soil water content under sparse vegetation and changeable sky conditions: comparison of two thermal inertia approaches

A critical analysis of a thermal inertia approach to map surface soil water content on bare and sparsely vegetated soils by means of remotely sensed data is reported. The study area is an experimental field located in Barrax, Spain. In situ data were acquired within the Barrax 2011 research project. An advanced hyperspectral scanner airborne imager provides images in the visible/near-infrared and thermal infrared bands. Images were acquired both in day and night times by the Instituto Nacional de Tecnica Aeroespacial between 12th and 13th of June 2011. The scene covers a corn irrigation pivot surrounded by bare soil, where a set of in situ data have been collected both previously and simultaneously to overpasses. To validate remotely sensed estimations, an ad hoc dataset has been produced by measuring spectra, radiometric temperatures, surface soil water content, and soil thermal properties. These data were collected on two transects covering bare and sparsely vegetated soils. This ground dataset was used (1) to verify if a thermal inertia method can be applied to map the water content on soil covered by sparse vegetation and (2) to quantify a correction factor accounting for solar radiation reduction due to sky cloudiness. The experiment intended to test a spatially constant and a spatially distributed approach to estimate the phase difference. Both methods were then applied to the airborne images collected during the following days to obtain the spatial distribution of surface soil water content. Results confirm that the thermal inertia method can be applied to sparsely vegetated soil characterized by low fractional cover if the solar radiation reaching the ground is accurately estimated. A spatially constant value of the phase difference allows a good assessment of thermal inertia, whereas the comparison with the three-temperature approach did not give conclusive responses. Results also show that clear sky, only at the time of the acquisition, does not provide a sufficient condition to obtain accurate estimates of soil water content. A corrective coefficient taking into account actual sky cloudiness throughout the day allows better estimates of thermal inertia and, thus, of soil water content.

Consistency of the National Realization of Dew-Point Temperature Using Standard Humidity Generators

The comparison of two high-range standard humidity generators used by Instituto Nacional de Tecnica Aeroespacial to realize dew-point temperature in the range from −10 °C to +95 °C has been performed using state-of-the art transfer standards and measurement procedures, over their overlapping range from −10 °C to +75 °C. The aim of this study is to investigate the level of agreement between the two generators, to determine any bias, and to quantify the level of consistency of the two realizations. The measurement procedures adopted to minimize the effect of the influence factors due to the transfer standards are described, and the results are discussed in the context of the declared calibration and measurement capabilities (CMCs).

A Sol–Gel based magneto-optical device for the NANOSAT space mission

On December 2004, the Spanish Space Agency INTA (Instituto Nacional de Tecnica Aeroespacial) launched the first nanosatellite called NANOSAT (Fig. 1) on board an European rocket Ariane 5, from the French Guyana. The satellite consists of a hexagonal device of <19 kg of weight with a diameter of about 50 cm, which describes a LEO orbit of 655 km of altitude. The main objective of the satellite is to probe the operation and performance of micro- and nanotechnologies in space environment. One of the scientific experiments implemented on board was the Sol–Gel based magnetic nanosensor. Open image in new window Fig. 1 NANOSAT 01

The New INTA High-Range Standard Humidity Generator and Its Comparison with the Austrian National Humidity Standard Maintained at BEV/E+E

A EUROMET collaborative project has been set up between Instituto Nacional de Tecnica Aeroespacial (INTA) and E+E ELEKTRONIK Ges.m.b.H, the two designated laboratories of the Spanish and Austrian National Metrology Institutes, Centro Espanol de Metrologia (CEM) and Bundesamt fur Eich- und Vermessungswesen (BEV), respectively. The objective of the project is to provide INTA with a new standard that covers the dew-point temperature range from − 27°C to +90°C with a gas flow up to 5 L· min−1 in the “two-pressure” mode, extended to 95°C when operated as a continuous flow “single-pressure” generator, and investigate the importance of the enhancement factors in the uncertainty estimations used in support of the participants’ calibration and measurement capabilities (CMC) (The CIPM Mutual Recognition Arrangement, http://www.bipm.fr/en/cipm-mra/). The equivalence of the Spanish and Austrian national standards is also to be evaluated, further supporting the outcomes of the Key Comparisons, in which both have already participated. The preliminary results obtained to date are reported and discussed in the context of the project and the consistency of the declared CMC’s.