نشریه علوم و فناوری فضایی
سال شانزدهم شماره 4 (پیاپی 59، زمستان 1402)

In this paper, a robust adaptive hybrid control approach based on a combination of super-twisting and non-singular terminal sliding mode control (STNSMC) approaches for vibration and attitude control of a flexible spacecraft with fully coupled dynamic is developed. The proposed adaptation law eliminates the need for bounds knowledge of external disturbances and uncertainties. Then an ST-based NSMC generates a continuous control signal to reject the Chattering phenomenon, the non-singular terminal switching control law with the ability to generate continuous control commands to eliminate the chattering phenomenon. Moreover, finite-time convergence is achieved, and the singularity problem has been avoided. The overall stability of the system has been demonstrated using the Lyapunov theory. One of the essential features of the proposed control algorithm is to prevent overestimation of control gains and faster convergence rates comparing to conventional ST and non-singular terminal SMC approaches. The simulations in the form of a comparative study for large-angle maneuver reveal the advantage of the proposed approach.

One of the damaging factors for the proper functioning of telecommunication payloads are high energy ionizing particles in space, which the use of proper shield is a way to deal with it. In the design of protection, several factors, such as the type of part and the amount of weight acceptable for the payload.etc.must be taken into consideration. In recent years, in order to reduce the costs of construction and launch, the use of non-space components has been favored.Therefore, the use of shields with the suitable material in with radiation resistance, with respect to the weight budget considerations, will be one of the important challenges .In this paper, the aim is to investigate the methods of reducing the weight budget considering with respect to the radiation damage of ionizing dose. In this regard, a five-year technology development mission in the GEO orbit has been predicted, and the results of simulations and testing of aluminum and polyethylene shielding to check ionizing dose damage, according to the initial and reference weight budget, have been presented and compared. The analysis and evaluation of the test results using polyethylene protection shows a 17.21 percentage reduction between the two external and internal radiation meters.

The national information network is being implemented with the aim of providing the services needed by the people through internal infrastructure and independent of international internet platforms. Considering the geographical diversity of the country and in order to increase the reliability coefficient and access penetration coefficient in the national information network and also due to the needs of future services, it is not possible to rely solely on fiber and the use of satellite communications will be unavoidable. At present, satellite communication has not reached a worthy position in the country's communication network and is limited to some applications such as banking, oil and gas etc. However, due to the development of broadband networks and the increasing need for high-speed data transmission and the increase in data volume, as well as creating social justice and increasing the speed of access, as well as the Internet penetration rate in the country in order to access various services, it is necessary to develop satellite communications to should be taken seriously. In this regard, an analysis of the market of several categories of services in Iran has been done so that the amount of gap in the amount of service provision and the amount of need to receive services can be seen.

In this research, the dynamic response of a U-12 CubeSat (20x20x30 cm) is investigated for three configurations during the launch conditions. Despite the existence of a successful design for this satellite, adding a mount to install on a standard adapter, the structural design of the satellite has been modified for modal computability with the launcher., which is based on 3 general approaches: to apply geometric changes to the structure, changing the extent of the points to improve the limitations of connecting to the launcher, and rearranging the internal system components regarding the standards and principles of compatibility and proximity. Therefore, more than the addition of the adapter mount and a few changes in the separating plates, a spire has been added to the structure, which has caused a change in the internal arrangement, including the halving of the fuel tank (by reducing the capacity of 595 cubic centimeters). Despite the increase of 370 grams of total mass, the natural frequencies of the system have been increased enough without the need for redesign and there will be no frequency interference with the frequency spectrum of the launcher.

One of the attitude sensors for the spacecraft is the star sensor. The attitude calculation by the star sensor includes several steps: image processing, star identification, database search, and implementation of the attitude determination algorithm. This paper presents analysis and improvements on the star identification algorithm based on singular value decomposition. To improve the identification results, modifications have been made to the algorithm. Also, analysis and simulation are presented to investigate the effect of field of view dimensions and the number of stars used on the identification results, and the rate of duplicate sets in the database. In addition, identification has been considered a two-step process based on singular values and vectors. The results show the superiority of the improved algorithm in increasing the identification rate and reducing the rate of duplicate sets in the database. The identification rate of the improved algorithm in 〖10〗^°×〖10〗^° and 〖12〗^°×〖12〗^° fields of view dimension is always more the %97. The simulations were performed based on the Hipparcos star catalog for stars brighter than magnitude 6.5 and using MATLAB software.

In this article, a new type of EBG structure known as frequency selective surface (FSS) with reconfigurable capability is investigated. The proposed design introduces a new adjustable band stop filter equipped with PIN diodes. Operating frequency of the FSS structure is in the C-band and in the frequency range of 4GHz to 8GHz, which at the central frequency of 4.75GHz, provides a bandwidth of about 1 GHz, when the state of the diode being on. The center frequency of this filter is shifted to 5.23 GHz when the diode is off. In fact, this structure is supposed to be used as a type of electromagnetic coating filter for space payload in the next generation satellites. After the design and simulation of the final cell, an equivalent circuit model is also presented to confirm the design and simulation. These structures protect electronic modules of satellite payload against electromagnetic radiation, electronic warfare. The RCS reduction is the other application of the FSS structure.

Seed aging is a process that can lead to a complete loss of seed viability. This process occurs when seeds are exposed to long-term storage or controlled deterioration treatments such as excessive dryness, lack of oxygen, and temperature fluctuations on Earth or in outer space. Proteomic changes can occur in the dry state of seeds. Extreme temperature fluctuations in outer space, especially on the moon and Mars, are one of the most important challenges for space scientists to transfer plant seeds and grow them in outer space outside the atmosphere. The present study studied the effects of simulated space temperature fluctuations on the quantitative and qualitative content of dry tomato seed proteins. The results showed 13 protein bands in the molecular weight range of 8.89 to 91.82 kilodaltons. A double or more significant decrease in the intensity of protein bands with high molecular weight was also observed in the treated group compared to the control. Finally, the two-dimensional electrophoresis technique followed by mass spectrometry is suggested for better resolution of tomato seed proteins and their better separation, as well as identification of unknown protein bands in future studies.