Wahyudi Hasbi

Abstrak Sistem hubungan ke bawah (down-link system) merupakan bagian integral dari sistem penting pada sebuah stasiun bumi (ground station) di samping sistem lainnya. Sistem hubungan ke bawah pada stasiun TT&C LAPAN-ISRO Biak berfungsi menangani penerimaan sinyal telemetri satelit. Hingga saat ini sistem tersebut telah beroperasi dengan baik bahkan telah beberapa kali menangani momentum-momentum penting seperti pada saat fase awal peluncuran satelit dan bahkan pemantauan data telemetri roket peluncur (Launch Vehicle Satellite) ISRO (Indian Space Research Organisation).

In this paper, a study on the impact of changing the space-based Automatic Identification System (AIS) monopole antenna orientation on its message reception performance in orbit has been conducted. The study has been carried out by maneuvering the attitude of LAPAN-A2, an equatorial orbiting microsatellite with AIS antenna fixedly mounted on the satellite’s body, into the desired orientation. Based on the analysis of the datasets collected during the maneuver, the orientation of AIS monopole antenna 45° toward its flight direction increases the overall detection performance of the AIS message, including class A ship to 208.80% and also class B ships to 175.93%. This orientation also increases the detection of AIS messages in ocean areas having low detection probability due to AIS signal collision. The result of this research could become a reference in order to specify AIS antenna position and orientation in a small satellite carrying a space-based AIS system for maritime surveillan...

ABSTRACTOBDH (On-board data handling) is a satellite subsystem that receives, processes, decides and executes commands from and to satellites. OBDH is built on two systems namely hardware and software integrated system (firmware system). In terms of hardware, OBDH uses a processor with 32bit RISC architecture, 128/256 Kbyte internal memory and a firmware system that is built using primitive programming. This programming uses the super loop architecture program and interrupt to manage the system to function properly. Problems occur when an error occurs in one of the functions in the interrupt routine resulting in failure of interpretation of commands or data from satellite sensors. This paper describes the implementation of the error patching methods on the LAPAN-A3/IPB Satellite OBDH firmware system in order to keep the system working well. Initial verification through testing on the ground have been successfully performed using engineering model of OBDH and hardware in the loop sim...

Nitrogen content is an important indicator used for monitoring and management of plant due to its role in photosynthesis, productivity as well as its effect on carbon and oxygen cycle. The research aimed at estimation of nitrogen content of rice crop based on Near Infrared (NIR) reflectance using Artificial Neural Network (ANN). ANN is a non-linear modeling tools based on statistical data. Nitrogen content was measured by laboratory analysis, meanwhile, its spectral reflectance of NIR (700 – 1075 nm) in the field was measured by using hand held spectroradiometer. Data were divided into 33 data training and 15 data testing using 3-fold cross validation. We found that organic molecules (nitrogen, water, etc) have specific absorption pattern in the NIR region. The experimental result shows that the comparison between measured and model estimation of Nitrogen content have RMSE of about 0.32. We conclude that NIR reflectance values can be used to predict nitrogen content using ANN method.

... Stasiun TT & C LAPAN-ISRO Biak kemudian dilengkapi dengan sub reflektor yang mampu menjalankan up & downlink dalam ... Salah satu faktor utama performa stasiun adalah G/T sehingga dengan penambahan kapabilitas tersebut di-harapkan tidak akan menyebabkan ...

This article elaborates a processing chain devised to recognize the ships existing on medium resolution multispectral imageries (MSI). The chain consists of the following three steps. Firstly, an adaptive local saliency mapping technique is instigated on open ocean regions to obtain all floating objects. Secondly, to extract the ship candidates, two-step verification is applied based on specific spectral and geometric information of the ships. Lastly, a calculation to determine the properties of the ships, including their length, breadth, and heading, is then carried out. Furthermore, we propose a novel method for correcting miscalculated ship heading; by combining wake segmentation and Radon Transform (RT) approaches to locate the position and estimate the length of the wake generated by the ships. With the detected wake length, ship velocity can also be assessed. The developed chain is then tested using imageries acquired by LAPAN-A3 microsatellite, and the results are compared to those reported by the Automatic Identification System (AIS). Experimental results indicate that the proposed chain achieves higher detection performance and can produce better heading information compared to the existing methods.

Performance of LAPAN-A2 and LAPAN-A3 space-based Automatic Identification System (AIS) have been successfully assessed as the satellites operated at individual and two-satellites constellation modes. Since LAPAN-A2 and LAPAN-A3 respectively orbiting at 6 • and 97 • of inclination, they form a unique constellation; hence, assessment on AIS performance from this equatorial-polar constellation is unprecedented. The assessment is intended to measure both the system and receiver performance of space-based AIS. The measurement of system performance calculates the capability of a space-based AIS system in re-detecting a ship as it moves globally. This performance is used to analyze whether the satellite and its AIS payload are systematically well-configured, including its orbital properties, antenna placement, and receiver's ability. The measurement of receiver performance is aimed to analyze the receiver capability in detecting all existing ships transmitting the AIS messages. This performance is represented as the ratio between the number of ships detected by the space-based AIS receiver and an ideal AIS receiver. In our case, massive AIS messages collected by an integrated space-terrestrial AIS receiver network has been used as the benchmark. By using 31 days of the collected AIS dataset, operating the satellites as a constellation increases the system and receiver performance by a factor of 7.56% and 7.93%, respectively. The further result shows that the constellated AIS receiver performs excellently in the deep-sea regions, with the value of system performance ranging from 95% to 100%. Moreover, the receivers of constellation satellites overperformed the benchmark receiver on up to 61.84% of their full coverage. The main contribution of this research is to provide information related to the advantages of operating equatorial-polar AIS constellation regarding its in-orbit performance. The results could become a reference in developing a space-based maritime surveillance tool with excellent performance and frequent accesses in those regions. INDEX TERMS LAPAN-A2, LAPAN-A3, space-based AIS, performance, satellite, orbit.

Indonesian satellite operations are mainly known for the operation of geostationary orbit (GSO) satellites for telecommunication missions. In the last decade, however, the activities of non-GSO satellites in Indonesia are significantly increasing. Therefore, the objectives of this research are to find out the cause of the growth and to predict the future operation of non-GSO satellites in Indonesia. For such purpose, review on the operation of non-GSO satellites in the past and now was done. Analysis on the characteristics of their missions, owners/operators, and technical characteristics of the satellites were done. Literature studies on the global trends and their defining strategic environments were also done to complete the insight. The study shows that increase in the use of non-GSO satellites is caused by the growth in remote sensing application, M2M application, and development of LAPAN's satellites. In the future, the growth of non-GSO remote sensing satellite is predicted to be caused by the same reason. The increase in the use of non-GSO telecommunication satellites, however, will be affected more by the new global trend. The increase in non-GSO remote sensing satellites does not affect significantly on the needs of frequency and ground stations. The increase in the non-GSO telecommunication satellites, however, needs significant additional frequency allocations and ground stations.

In this paper, a study on the impact of changing the space-based Automatic Identification System (AIS) monopole antenna orientation on its message reception performance in orbit has been conducted. The study has been carried out by maneuvering the attitude of LAPAN-A2, an equatorial orbiting microsatellite with AIS antenna fixedly mounted on the satellite’s body, into the desired orientation. Based on the analysis of the datasets collected during the maneuver, the orientation of AIS monopole antenna 45° toward its flight direction increases the overall detection performance of the AIS message, including class A ship to 208.80% and also class B ships to 175.93%. This orientation also increases the detection of AIS messages in ocean areas having low detection probability due to AIS signal collision. The result of this research could become a reference in order to specify AIS antenna position and orientation in a small satellite carrying a space-based AIS system for maritime surveillance & monitoring purposes.

A method for uncertainty evaluation of vicarious calibration for solar reflection channels (visible to near infrared) of spaceborne radiometers is proposed. Reflectance based at sensor radiance estimation method for solar reflection channels of radiometers onboard remote sensing satellites is also proposed. One of examples for vicarious calibration of LISA: Line Imager Space Application onboard LISAT: LAPAN-IPB Satellite is described. Through the preliminary analysis, it is found that the proposed uncertainty evaluation method is appropriate. Also, it is found that percent difference between DN: Digital Number derived radiance and estimated TOA: Top of the Atmosphere radiance (at sensor radiance) ranges from 3.5 to 9.6 %. It is also found that the percent difference at shorter wavelength (Blue) is greater than that of longer wavelength (Near Infrared: NIR). In comparison to those facts to those of Terra/ASTER/VNIR, it is natural and reasonable.