Jurnal Sains Dirgantara
Not a member yet
243 research outputs found
Sort by
EVOLUSI ORBIT CENTAURS DAN TRANS-NEPTUNUS KE BAGIAN DALAM TATA SURYA
Get PDFDynamical study of Trans-Neptunian Objects (TNOs) showed that the orbital evolution of TNOs, especially for Scattered-Disk class, is closely related to Centaurs. As of 1 June 2009, there were 673 known Centaurs and TNOs whose orbits are well-determined within an uncertainty of ï‚£ 6.4 ï‚¢/decade. It is interesting to investigate a fraction of evolving Centaurs and TNOs to inner solar system regions along 1 Myr evolution under perturbations of all planets. In order to have a better knowledge about spatial distributions of Centaurs and TNOs, we generated additional four sets artificial data based on the known distribution. We find that most Centaurs show chaotic orbital evolutions and many of them are ejected out to the outer solar system. The ejected Centaurs in the first-half evolution are more numerous than that of the second-half one. This study also indicates that number of Centaurs originated from 3:2 Neptune resonance objects is more abundant at about 5 ï‚´ 105 yr, and only ~1% Centaurs and TNOs evolve to be Mars-crossers. Keywords: Asteroids, Orbit dynamic, Centaurs, Trans-Neptunu
ANALISIS PENYEBAB ANOMALI SATELIT AKIBAT AKTIVITAS GEOMAGNET
Get PDFAnalisis terhadap data anomali satelit dan aktivitas geomagnet melalui indeks Kp dari tahun 1990-2001 memberikan informasi prakiraan penyebab dan dampak pengaruh aktivitas geomagnet ini pada operasional satelit. Analisis ini menunjukkan bahwa 58 persen kejadian anomali satelit dalam kurun waktu 1990-2001 kemungkinan disebabkan oleh aktivitas geomagnet. Hal ini dapat dilihat melalui besarnya indeks Kp pada saat kejadian dan rentang waktu 3 hari sebelum dan sesudah kejadian anomali dilaporkan. Variasi aktivitas geomagnet ini menimbulkan dampak yang berbeda pada sistem satelit, mulai dari kerusakan yang bisa langsung dipulihkan (recovery) dari stasiun bumi maupun kegagalan misi satelit secara total (total loss). Analisis ini juga memperlihatkan bahwa kebanyakan anomali satelit dialami oleh instrumen yang terdapat dalam sistem GNdanC (Guidance, Navigation and Control) satelit seperti sistem kontrol sikap satelit (ACS), sistem pengarah (pointing system) dan sensor pada satelit. Kata kunci: Satelit, Anomali satelit, Indeks Kp
TELAAH AWAL KEUBAHAN SETENGAH SUMBU PANJANG AKIBAT EFEK YARKOVSKY PADA ASTEROID 3362 KHUFU (1984 QA)
Get PDFEfek Yarkovsky adalah gaya non-gravitasional yang bekerja pada benda yang disebabkan oleh emisi anisotropik foton termal, yang memberi momentum bagi benda tersebut. Efek ini biasanya terjadi pada meteoroid atau asteroid berukuran kecil (dengan diameter 10 cm sampai 10 km). Tulisan ini mencoba meninjau efek Yarkovsky tersebut bagi asteroid 3362 Khufu (1984 QA) yang berdiameter 0.7 km, serta Bond-albedo 0.17. Efek Yarkovsky menyebabkan keubahan pada setengah sumbu panjang orbit, akibatnya eksentrisitas orbit juga berubah. Terjadinya perubahan pada elemen orbit memberikan peluang asteroid tersebut bergerak mendekati Bumi. Telaah ini menunjukkan amplitudo keubahan setengah sumbu panjang orbit terhadap waktu akibat komponen harian dan musiman, masing-masing maksimal adalah 1.3×10-5 m/detik dan -3.7×10-9 m/detik. Kata kunci: Efek Yarkovsky, Asteroid, Orbit
PREDIKSI JANGKA PENDEK BULANAN JUMLAH FLARE DENGAN MODEL ARIMA (p,d,[q]), (P,D,Q)132
Get PDFThe time series of the monthly of flares from January 1965 to December 2004 is analyzed by ARIMA models. It is suggested that there is any auto correlation between monthly data in regular and seasonal order (11 years solat activity cycle) in the ARIMA (p,d[q]), (P,D,Q)132 models. After several of feasibility test had successed and the assumption of stationary in mean and variance was obtained, we can determine the model i.e; ARIMA (1,1,[13])(0,1,1)132 and ARIMA (0,1,[13])(0,1,1)132. From this models, we can use to predict the monthly number of flares
MODEL PELURUHAN DAN REENTRI ORBIT SATELIT LEO
Get PDFBased to the non-central Earth's gravity causing the sekuler variation on the semi mayor axis and ecentricity of the LEO's satellite the software of orbital decay has been developed. The input for the software is the height, eccentricity existed in TLE (Two Line Elemen table), anapproximated ballistic coefficient and the atmospheric density on virous solar activity. The software has been used to predict the time is to 10%, and the error will become smaller if the software is executed closed to reentry time such a week before satellite reentry. The softaware can be used to approximate the ballistic coefficient of a satellite
ESTIMASI PARAMETER TURBULENSI UNTUK JASA PENERBANGAN BERBASIS HASIL ANALISIS BEBERAPA DATA RADIOSONDE DI KAWASAN BARAT INDONESIA
Get PDFThe one of an important thing related to the aviation is the correct information of aviation meteorology, especially about bad weather condition such as turbulence that often disturb the plane during their flight. There are many parameters to estimate the turbulence parameter. One of them is called the Richardson Number (Ri) such as already investigated by Waco (1970). We continued hos study by applying the radiosonde data distributed at five stations in the Western part of Indonesia region, especially during the Coupling Processes Equatorial Atmoephere I (CPEA I) Campaign started from April 10 to May 10, 2004. We defined the turbulence when Ri less more 0.25 as described by Killer (1981). We found initial turbulence occurrence indication, even though we have found significant indication yet, related with less of locations and data observations which is only one month observation. Turbulance in the plane is described as the changes of vertical gravitation in the plane and observed by vertical accelerometer which is installed in the plane. After making some validations with the vertical accelerometer data, we found only a few good correlation between Ri and turbulence. We suspect it caused by the less of data observation. But initial indication based on data analysis shows that light turbulence occurrence a long Eastern Coast of Malacca Peninsula on 19th April 2004
PEMODELAN TLCL DAN TCCL UNTUK KOTA BANDUNG DENGAN MENGGUNAKAN METODE SKEW-T PLOTTING
Get PDFSimple model has been made to predict temperature of LCL and CCL based on surface on surface dew point data. The method which used is skew-T plotting, i.e. plotting temperature and dew point profile of radiosonde data on aerogram paper. The data which used is radiosonde sounding data of Bandung in 1992, 1995, 1997 and 1999. Model formula which obtained has linear form, when surface dew point straight proportional to LCL and CCL temperature. CCL and LCL temparature modelling based on surface humidity data has been made natural logarithmic of surface humidity. LCL temperature has good correlations to CCL temperature, and generally form linear and straight proportional
METODE BARU PRAKIRAAN SIKLUS AKTIVITAS MATAHARI DARI ANALISIS PERIODISITAS
Get PDFPeriodicity analysis indicates that sunspot number is better to be used as the base of solar activities prediction. The main periodicity (of about 11 years) is relatively constant so thatit can be used in long-term prediction several cycles ahead. For prediction, wavelet analysis of all domonant periode has to be done on any cycle to be used in reconstructing the cycle pattern and for predicting the next ones. The relationship between length of cycle and maximum amplitude is used to predict the peak of a cycle. Prediction tests of several cycles indicate that this new method is accurate enough in predicting cycle pattern and maximum amplitude several cycles ahead. The ability in predicting several cycles ahead may be the superiority of this method over the precursor method considered to be relatively the most accurate nowadays
PEMANFAATAN GLOBAL CIRCULATION MODEL (GCM)UNTUK PREDIKSI PRODUKSI PADI
Get PDFDalam pengembangan model untuk prediksi produksi padi berdasarkan Palmer Drought Severity Index (PDSI) menggunakan luaran GCM CSIRO MK3 (Commonwealth Scientific and Industrial Research Organization) Australia, dengan input curah hujan dan suhu bulanan untuk tiga skenario SRES (Special Report on Emissions Scenarios) yaitu SRESA2, SRESB1 dan SRESA1B, maka dapat diprediksi produksi padi di dua Kabupaten Subang dan Tasikmalaya. Dengan menghitung luas area pertanian pada masing-masing wilayah ZPI (zona prediksi iklim), PDSI terboboti per subround/periode (PDSIWp) dan penentuan bobot berdasarkan persentase luas area pertanian pada setiap wilayah maka diperoleh prediksi produksi padi di masa yang akan datang (2010, 2020, 2030, 2040, dan 2050). Prediksi produksi padi di Kabupaten Subang sebesar 792.943 ton dari rataan ketiga model skenario Pemanfaatan Global Circulation........ (Sinta Berliana Sipayung et al.) 83 GCM pada tahun 2020, sementara pada tahun 2050 prediksi produksi padi sebesar 827.270 ton. Kabupaten Tasikmalaya rataan produksi padi periode 1988-2005 adalah 568.145 ton per tahun, sedangkan prediksi produksi padi tahun 2020 sebesar 573.906 ton dan 596.026 ton pada tahun 2050. Jika dibandingkan produksi saat ini rataan tahun 1988-2005 prediksi produksi padi mengalami penurunan sekitar 8 % pada tahun 2020 dan 4% tahun 2050 di Kabupaten Subang sedangkan Tasikmalaya mengalami kenaikan 1% pada tahun 2020 dan 5% pada tahun 2050. Kata kunci: Iklim, GCM, PDSI dan Produksi Padi