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 – 1075nm) 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

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.

Images captured by Lapan-A3 pushbroom imager will have some geometric distortions from various sources. Most of them can be ideally corrected by using a high quality ancillary data, i.e. Lapan-A3 attitude sensor must provide attitude data for each image line (2,5ms) and free from measurement error. That ideal condition is nearly impossible to achieve so this paper aims to determine the minimum performance of Lapan-A3 ADCS (Attitude Determination and Control System) so that the image captured can still be well corrected with systematic geometric correction software. Three aspects being evaluated are accuracy and sampling frequency of attitude sensor, as well as the stability mode of ACS. Simulation results show that 10 Hertz sampling frequency of attitude data is needed when ACS closed loop mode is used, while 1/3 Hertz sampling frequency is enough when ACS open loop mode is used. Accuracy of attitude sensor should be better than 0,003° for pitch/roll axis and 0,02° for yaw axis. Related with ACS stability mode, image correction is way easier if observation is done under open loop mode since in closed loop mode there will be random jitter error. If the observation is done under closed loop mode then ACS should have pointing stability of 0,002°, far from current Lapan-A3 ACS pointing stability under closed loop mode, which is 0,1°.

The Controller Area Network (CAN) is a vehicle bus standard which allows various electronic components such as microcontrollers, sensors, actuators to communicate with each other without a host computer, with speed up to 1Mb/s. It is a message-based protocol designed specifically for automotive, but it is also used in areas such as aerospace, maritime, and industrial automation. The new satellite generation of LAPAN, LAPAN-A4, will carry payload Medium Resolution Multispectral Imager/SLIM4 and the interface of this payload utilizes CAN bus communication. This paper is aimed at the design and implementation of CAN using microchip MCP and microcontroller for being able to communicate with SLIM4 over CAN Bus. For hardware design, the CAN controller used in this research is MCP 2515 and the CAN transceiver is MCP 2551 which uses the SPI interface to widen CAN Bus interface. From the result of the design and implementation, we got bit rate 388.042 Kbit/s by using internal oscillator 14.7456 Mhz without baud rate prescaler (BRP), the total bit time is 19 Time Quantum (T ₀ ) which consists of 1 T ₀ for synchronization segment, 7 T _O for propagation segment, then 8 T ₀ for phase segment1 and 3 T ₀ for phase segment2, respons time acknowledgement average is approx 403-405 ms, and the final configurations we choose for the baud register MCP 2515 are CNF1×0x00, CNF2=0xBE, and CNF3×0x02.

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.