Lean Satellite Concept

In 2014, International Academy of Astronautics (IAA) initiated Study Group (SG) 4.18, Definition and Requirements of Small Satellites Seeking Low-Cost and Fast-Delivery . Its objectives of the study group are to examine the definitions of small satellites, identify the requirements every satellite should follow and then reflect some of the findings to an ISO standard draft ISO/WD/20991, Space systems - Requirements for Small Spacecraft that is being developed recently at ISO/TC20/SC14. The purpose of the present paper is to present the latest findings in the SG activity especially in terms of small satellite definition. During the SG meeting in 2014, a round-table discussion was held to discuss the terminology to describe small satellites. The majority of the opinions were that neither mass nor size is suitable for defining small satellites. Rather, philosophy of design, manufacturing, mission, program management, etc., should be used for the definition. The round-table discussion came to the conclusion that the term Lean Satellite is more suitable than Small Satellite . Historically, the word of lean originated from Toyota Production System (TPS). There are few things in common between satellites and automobiles. It is very difficult to apply lean concepts as they are to satellites. But some concept of lean is necessary for satellites. New types of customers are emerging today who want more value from satellites through lower unit prices and faster system delivery. Currently, mega-constellations consisting of hundreds or thousands of satellites are being proposed. Traditional satellite development philosophy cannot be applied to mega-constellations because the total cost would be prohibitively high. Small satellites and mega-constellations can benefit from the application of the lean satellite concept, although it must be modified to accommodate the differences between satellites and automobiles. Space systems engineering has put emphasis on delivering a perfectly working system. On the other hand, lean concept has put emphasis on delivering a high-quality product with the minimum cost and shortest time. Developing the lean satellite concept can be an interesting new subject for space systems engineering. As a part of the SG activity, 16 questions were identified as good measures to scale the characteristics as a lean satellite. The 16 questions are made of 9 categories with different weighting. They are (1) total cost, (2) delivery time, (3) simplicity, (4) risk taking, (5) risk mitigation, (6) reliability requirement, (7) mission duration, (8) launch, and (9) waste minimization. Some categories are further divided to multiple questions. Each question has its weight. Each answer has its score. By adding the points of all the 16 questions, the total point is between 0 and 100. The questionnaire made of the 16 questions was distributed in SG and answers by more than 41 satellites from all over the world were collected. At the conference, the lean satellite concept will be presented more in detail along with the analysis of answers made by the 41 satellites

Nuevos registros de Selysiothemis nigra (Vander Linden, 1825) y Erythromma viridulum (Charpentier, 1840) de la isla de Cefalonia (Grecia) con una lista actualizada de la odonatofauna de la isla

Selysiothemis nigra (Vander Linden, 1825) and Erythromma viridulum (Charpentier, 1840) are recorded from the Greek island of Cephalonia for the first time, on the basis of photographic data. With the present note we also give an updated checklist of the odonatofauna for the island.Selysiothemis nigra (Vander Linden, 1825) y Erythromma viridulum (Charpentier, 1840) se citan en la isla griega de Cefalonia por primera vez, sobre la base de datos fotográficos. Con la presente nota también se proporciona una lista actualizada de la odonatofauna de la isla

Debris Cloud Evolution: Mathematical Modeling and Application to Satellite Constellation Design

Orbital break-ups produce a large number of fragments, which constitute an obvious hazard for other satellites in nearby orbits. Of these fragments, many are too small to be detected by ground-based facilities: this leads to the need for mathematical modelling as a tool for adequate risk analysis. In this paper an average spatial density model is presented. It is based on the Gauss analogy and, for unperturbed Keplerian orbits, it matches the asymptotic density model developed by other authors. Risk analysis for satellite constellations is an interesting application of debris cloud evolution models: the survivability of a constellation as a whole following the break-up of one of its satellites is obviously of primary concern in the constellation design. Risk analysis is conducted over a number of traditional configurations in order to achieve an additional constraint on the design parameters. Results indicate the remarkable influence of the fragmentation point position along the orbit; moreover, the higher risk for low orbit and the advantage of placing more satellites on a limited number of planes are assessed

Results of the attitude reconstruction for the UniSat-6 microsatellite using in-orbit data

UniSat-6 is a civilian microsatellite that was launched in orbit on the 19th of June, 2014. Its main mission consisted in the in-orbit release of a number of on-board carried Cubesats and in the transmission to the UniSat-6 ground station of telemetry data and images from an on-board mounted camera. The spacecraft is equipped with a passive magnetic attitude control system. Gyros and magnetometers provide the information about the attitude of the spacecraft. The importance of reconstructing the attitude motion of UniSat-6 lies in the dual possibility, for future missions, of:controlling the direction of ejection of the on-board carried satelliteshaving an accurate pointing for remote sensing operation.The reconstruction of the attitude motion of UniSat-6 is based on the data of the on-board Commercial Off The Shelf (COTS) gyros and magnetometers, downloaded at the passages over the ground station in Roma, Italy. At ground, these data have been processed with the UnScented QUaternion Estimator (USQUE) algorithm. This estimator is an adaptation of the Unscented Filter to the problem of spacecraft attitude estimation. The USQUE is based on a dual attitude representation, which involves both quaternions and Generalized Rodrigues Parameters. In this work, the propagation phase of the algorithm contains only a kinematic model of the motion of the spacecraft. This paper presents the results of the reconstruction of the UniSat-6 attitude using on-board measurements. The results show that the spacecraft effectively stabilized its attitude motion thanks to the on-board magnetic devices

Review 2: "Evaluating aerosol and splatter during orthodontic debonding: implications for the COVID-19 pandemic"

n/

REGULUS Electric Propulsion Module IoD in UniSat-7 Mission

T4i is a propulsion system company founded in 2014, originated from the Space Propulsion Group of University of Padua, Italy, and active in the market of small satellites. In the last decade T4i has been developing REGULUS, a cutting-edge electric propulsion system for in-space mobility fed with iodine propellant. REGULUS has been specifically designed for Cubesats and micro satellite platforms and it is based on a RF Magnetically Enhanced Plasma (MEP) thruster. Thanks to its standard interfaces it is conceived to be easily “plugged&played” into the satellite, without complex engineering procedures

The in vitro effect of different PRP concentrations on osteoblasts and fibroblasts

Objectives:The aim of this study was to assess the biological rationale for the use of platelet-rich plasma (PRP) by evaluating the effect of different concentrations of PRP on osteoblasts (OB) and fibroblasts (FB) function in vitro. Materials and methods:PRP was obtained from volunteer donors using standard protocols. Primary human cultures of oral FBs and OBs were exposed to both activated and non-activated plasma as well as various concentrations of PRP (2.5 x, 3.5 x and max (4.2-5.5 x)). Cell proliferation was evaluated after 24 and 72 h using an MTT proliferation assay. Production of osteocalcin (OCN), osteoprotegerin (OPG) and transforming growth factor beta 1 (TGF-beta 1) was evaluated in OB after 24 and 72 h. Statistical analysis was performed using one-way ANOVA. Results:PRP-stimulated cell proliferation in both OBs and FBs. The effect of different PRP concentrations on cell proliferation was most notable at 72 h. The maximum effect was achieved with a concentration of 2.5 x, with higher concentrations resulting in a reduction of cell proliferation. Upregulation of OCN levels and downregulation of OPG levels were noted with increasing PRP concentrations at both 24 and 72 h. TGF-beta 1 levels were stimulated by increasing concentrations of PRP, with the increased levels being maintained at 72 h. Conclusions:PRP preparations exert a dose-specific effect on oral FBs and OBs. Optimal results were observed at a platelet concentration of 2.5 x, which was approximately half of the maximal concentrate that could be obtained. Increased concentrations resulted in a reduction in proliferation and a suboptimal effect on OB function. Hence, different PRP concentrations may have an impact on the results that can be obtained in vivo

Surgical Management of Medication-Related Osteonecrosis of the Jaw Patients Related to Dental Implants

The aim of the present study is to report a case series of patients with peri-implant medication-related osteonecrosis of the jaw (MRONJ), in particular describing the onset of the condition and surgical treatment outcome

Soft Magnets for Passive Attitude Stabilization of Small Satellites

The spinning and oscillatory motions of small orbiting satellites can be damped exploiting the magnetic energy dissipation occurring in onboard soft magnetic strips, cyclically excited by the oscillation of the earth field component along their axis. In this paper we investigate the role played by the intrinsic magnetic properties of the material, the aspect ratio of the strips, and their mutual arrangement in achieving maximum energy dissipation under typical spacecraft working conditions. Grain-oriented Fe-Si, mumetal, and Fe-based amorphous alloys, all endowed with near-rectangular hysteresis loops, are considered. Their energy loss behaviour is calculated when, either as single strip samples or arranged into an array of strips, they are subjected to a slowly oscillating magnetic field of defined peak value, emulating the action of the earth magnetic field on the travelling satellite. The strip size and array layout leading to maximum energy loss are predicted. Amorphous alloys, combining high saturation magnetization with flexible hysteresis loop properties, are shown to lead to the best damping behaviour under both oscillating and spinning satellite motions. In the latter case the Fe-Si strips appear to provide comparably high damping effects, while inferior behaviour is always predicted with mumetal samples

High prevalence of human cytomegalovirus in a population of periodontally healthy subjects

Background: Human cytomegalovirus (HCMV) appears to be more frequent in periodontally affected patients than in healthy control groups. Based on this assumption, it has been suggested that HCMV may play a role in the pathogenesis of periodontal disease. Objective: The objective of this uncontrolled study was to assess the occurrence of HCMV in a large unselected population of periodontally healthy subjects. Study Design: Fifty consecutive periodontally healthy patients satisfied the inclusion criteria. Two samples of gingival crevicular fluids were taken from two non-bleeding on probing sites for each patient. Samples were collected from the anterior and the posterior area. Polymerase chain reaction (PCR) was used to identify the presence of HCMV. Results: HCMV was detected in 17 (33%) out of 50 participants. Ten subjects showed presence of HCMV on both anterior and posterior sites, whereas the remaining 7 only had HCMV present in the anterior sites. No differences were noticed between HCMV positive and HCMV negative in terms of smoking (p = 0.33), drinking habits (p=0,94) or the presence of prosthodontic restorations (p= 0,89). Conclusions: HCMV was detected in a high proportion of periodontally healthy subjects. Its presence was not found to be influenced by smoking or drinking habits