Pre-launch calibration results of the TROPOMI payload on-board the Sentinel-5 Precursor satellite

The Sentinel-5 Precursor satellite was successfully launched on 13 October 2017, carrying the Tropospheric Monitoring Instrument (TROPOMI) as its single payload. TROPOMI is the next-generation atmospheric sounding instrument, continuing the successes of GOME, SCIAMACHY, OMI, and OMPS, with higher spatial resolution, improved sensitivity, and extended wavelength range. The instrument contains four spectrometers, divided over two modules sharing a common telescope, measuring the ultraviolet, visible, near-infrared, and shortwave infrared reflectance of the Earth. The imaging system enables daily global coverage using a push-broom configuration, with a spatial resolution as low as 7×3.5&thinsp;km2 in nadir from a Sun-synchronous orbit at 824&thinsp;km and an Equator crossing time of 13:30 local solar time. This article reports the pre-launch calibration status of the TROPOMI payload as derived from the on-ground calibration effort. Stringent requirements are imposed on the quality of on-ground calibration in order to match the high sensitivity of the instrument. A new methodology has been employed during the analysis of the obtained calibration measurements to ensure the consistency and validity of the calibration. This was achieved by using the production-grade Level 0 to 1b data processor in a closed-loop validation set-up. Using this approach the consistency between the calibration and the L1b product, as well as confidence in the obtained calibration result, could be established. This article introduces this novel calibration approach and describes all relevant calibrated instrument properties as they were derived before launch of the mission. For most of the relevant properties compliance with the calibration requirements could be established, including the knowledge of the instrument spectral and spatial response functions. Partial compliance was established for the straylight correction; especially the out-of-spectral-band correction for the near-infrared channel needs future validation. The absolute radiometric calibration of the radiance and irradiance responsivity is compliant with the high-level mission requirements, but not with the stricter calibration requirements as the available on-ground validation shows. The relative radiometric calibration of the Sun port was non-compliant. The non-compliant subjects will be addressed during the in-flight commissioning phase in the first 6 months following launch.</p

The needs of foster children and how to satisfy them:A systematic review of the literature

Family foster care deeply influences the needs of children and how these are satisfied. To increase our knowledge of foster children’s needs and how these are conceptualized, this paper presents a systematic literature review. Sixty- four empirical articles from six databases were reviewed and categorized (inter-rater agreement K = .78) into four categories: medical, belongingness, psychological and self-actualization needs. The results give a complete overview of needs that are specific to foster children, and what can be implemented to satisfy these needs. This study shows psychological needs are studied more often compared to the other categories, which specially relates to much attention for mental health problems. Furthermore, most articles focus on how to satisfy the needs of foster children and provide no definition or concrete conceptualization of needs. Strikingly, many articles focus on children’s problems instead of their needs, and some even use these terms interchangeably. This review illustrates that future research should employ a proper conceptualization of needs, which could also initiate a shift in thinking about needs instead of problems

Psychosocial Needs of Children in Foster Care and the Impact of Sexual Abuse

Children in family foster care, especially those who have experienced sexual abuse, require a safe and nurturing environment in which their psychosocial needs are met. However, there is limited knowledge on how youth prioritize various needs and what impact previous experiences have on these needs. In this study, we asked youth (formerly) in family foster care to indicate their psychosocial needs, and analyzed if youth with a history of sexual abuse have different needs. A Q methodological study was conducted with 44 youth (age 16–28). Fifteen of them reported sexual abuse during their childhood. Using by-person factor analyses, respondents who share similar subjective views were grouped together. Qualitative interpretations of the factors show differences and similarities between and within the two groups, related to help from others, being independent, processing the past, and working toward the future. Although the needs of youth with and without experiences of sexual abuse seem mostly similar, one group of sexually abused youth specifically indicated not wanting an emotional connection to foster parents, but instead a strictly instrumental, professional relationship. This study captured the diverse perspectives of youth themselves, revealing that children in foster care differ with regard to what they consider as (most) important safety, belonging, self-esteem and self-actualization needs

Filtering techniques for orbital debris conjunction analysis

The steadily growing amount of orbital debris increases the probability and amount of collisions between two objects in orbit about the Earth. These collisions in turn create even more debris, and it is therefore important to keep track of future conjunctions. The U.S. Space Surveillance Network (SSN) uses ground- and space-based sensors to observe and track objects of about 10 cm and larger, of which the orbital information is coded in Two-Line Element (TLE) sets and listed in a catalog currently containing about 20,000 objects, which is partly distributed to the public. Using this TLE data, the Simplified General (and Deep-space) Perturbations 4 (SGP4/SDP4) analytical propagator is used to propagate the orbits of these objects, and includes secular, long-period and short-period perturbations due to the Earth's gravity field including J2, J3 and J4 and resonance effects for 12- and 24-hr orbits, as well as perturbations due to atmospheric drag, solar radiation, and gravitational attraction of the Sun and the Moon. The propagated orbits are used to predict conjunctions of pairs of objects. However, due to the large and increasing amount of objects in the catalog, numerically analysing all pairs would be too time-consuming. Therefore, numerous fast filters and sieves were designed to limit the search space of conjunction analysis, by discarding object pairs that are proven to never be able to conjunct. Four implementations of the classical perigee-apogee filter, next to six sieves with a new fine conjunction detection method, were analysed, implemented, and tested in terms of performance. The filter makes use of the altitude band of an object, and can be applied pre-hand. A method based on minimum and maximum radius determined from ephemerides, was found to be the most accurate and reliable in long-term application, while being able to be fine-tuned to the performance needs of a conjunction analysis process. Increasingly complex sieves are subsequently applied to the ephemerides at each time instance in a time interval, in order to efficiently discard object pairs. Eight possible improvements to the underlying theory and application of these sieves were made, resulting in one optimal combination of these improvements, and eventually resulting in a conjunction analysis system that is almost three times as fast as the best found reference method.Astrodynamics and Space MissionsSpace EngineeringAerospace Engineerin

Types of Cenozoic Mollusca from Java in the Martin Collection of Naturalis

An updated type catalogue of the Martin Collection (fossil Mollusca, predominantly from the Cenozoic of Java, Indonesia) is presented. Type specimen data, updated locality data, and illustrations are given