Jenni Virtanen | Finnish Geodetic Institute (original) (raw)
Papers by Jenni Virtanen
Bulletin of the American Astronomical Society, Aug 30, 1999
Bulletin of the American Astronomical Society, Nov 1, 2001
We have carried out a study of the orbits of the trans-Neptunian population. We have applied opti... more We have carried out a study of the orbits of the trans-Neptunian population. We have applied optimized statistical ranging to all the known objects ( 450, as of September 2001). The stability of the computed orbits has been secured by performing an analysis of the close encounters with the major planets. Together with a statistical analysis of the orbital element distributions, we address the problem of dynamical classification and the evolution of ephemeris uncertainty. In particular, we find that the orbital element distributions for the most numerous single-apparition TNOs do not suggest the existence of a sharp edge for the belt near 50 AU. We also provide refined ephemeris predictions for the poorly observed TNOs.
Planetary and Space Science, 2015
Advances in Space Research, 2015
Meteoritics & Planetary Science, 2014
Journal of Geodynamics, 2009
The monthly variation in the water mass of the semi-enclosed Baltic Sea is about 60 Gt RMS over a... more The monthly variation in the water mass of the semi-enclosed Baltic Sea is about 60 Gt RMS over an area of 390,000textrmkm2390,000 \textrm{km}^2390,000textrmkm2 . The Baltic has a dense network of tide gauges (TGs), and several high-resolution regional hydrodynamic models, making it one of the best-monitored seas for mass variations of this size in the world. We investigate the performance of different GRACE gravity field solutions to recover this oceanic mass variation using in situ measurements of sea-level heights. For GRACE, we use both the standard monthly solutions as well as regional solutions to estimate the total water storage in the Baltic Sea. For the “ground truth”, we use sea-level measurements in the network of tide gauges around the Baltic Sea. For comparison, we have access to data from two hydrodynamic models. The water mass estimated from the constructed sea surfaces is then compared with different GRACE estimates. At present, we ignore the steric anomalies, as they are small in the Baltic Sea. We also discuss the “leakage” between land hydrology and the Baltic Sea in the GRACE estimates of water storage.
We report 8 years of previously unpublished photometric observations of FK Com. The observations ... more We report 8 years of previously unpublished photometric observations of FK Com. The observations have been carried out between 1993 and 2001 with six different telescopes: 60 cm at Mt. Maidanak (Tashkent, Uzbekistan), Phoenix 10, Wolfgang and Amadeus located in Arizona, USA, and 20cm and 60 cm KVA on La Palma, Spain. Observations contain measurements at the following bands: Johnson U, B, V and R, Bessel R, Cousins I and Stromgren b and y. The observations are differential photometry in respect to the primary comparison star HD 117567. NOTE: Table 1 in the paper contains some small misprints in the Julian dates. Also for Wolfgang and Amadeus the number of observations given in Table1 at each band is slightly less than actually given in Table2c and Table2d. This is caused by accidentally using a limiting error of 0.01 in magnitudes when creating Table 1. In Table 2 the limiting error for Wolfgang and Amadeus is 0.02 mag, as mentioned in the paper itself. In Table2a-e 99.0000 means that no observations were available at that time at that band or that the error in the magnitude was larger than 0.02. (5 data files).
Monthly Notices of The Royal Astronomical Society, 2006
We present a statistical orbit computation technique for asteroids with transitional observationa... more We present a statistical orbit computation technique for asteroids with transitional observational data, that is, a moderate number of data points spanning a moderate observational time interval. With the help of local least-squares solutions in the phase space of the orbital elements, we map the volume of variation as a function of one or more of the elements. We sample the resulting volume using a Monte Carlo technique and, with proper weights for the sample orbital elements, characterize the six-dimensional orbital-element probability density function. The volume-of-variation (VOV) technique complements the statistical ranging technique for asteroids with exiguous observational data (short time intervals and/or small numbers of observations) and the least-squares technique for extensive observational data. We show that, asymptotically, results using the new technique agree closely with those from ranging and least squares. We apply the technique to the near-Earth object 2004 HA39, the main-belt object 2004 QR and the transneptunian object 2002 CX224 recently observed at the Nordic Optical Telescope on La Palma, illustrating the potential of the technique in ephemeris prediction. The VOV technique helps us assess the phase transition in orbital-element probability densities, that is, the non-linear collapse of wide orbital-element distributions to narrow localized ones. For the three objects above, the transition takes place for observational time intervals of the order of 10 h, 5 d and 10 months, respectively, emphasizing the significance of the orbital-arc fraction covered by the observations.
Proceedings of The International Astronomical Union, 2007
Canadian Journal of Physics, 2003
We present photometry of snow samples in the backscattering direction, i.e., at very small phase ... more We present photometry of snow samples in the backscattering direction, i.e., at very small phase (light-source - target - observer) angles. Relative brightness measurements are taken to study the backscattering behaviour of snow and ice samples to be able to interpret the opposition effect of icy solar-system surfaces (for example, icy rings and satellites). Preliminary results of three separate experiments are presented, all of which exhibit a similar feature: a backscattering peak is exhibited by snow of different grain types and with different amounts of contamination. The peak grows stronger with increasing contamination.
Advances in Space Research, 2006
Bulletin of the American Astronomical Society, Aug 30, 1999
Bulletin of the American Astronomical Society, Nov 1, 2001
We have carried out a study of the orbits of the trans-Neptunian population. We have applied opti... more We have carried out a study of the orbits of the trans-Neptunian population. We have applied optimized statistical ranging to all the known objects ( 450, as of September 2001). The stability of the computed orbits has been secured by performing an analysis of the close encounters with the major planets. Together with a statistical analysis of the orbital element distributions, we address the problem of dynamical classification and the evolution of ephemeris uncertainty. In particular, we find that the orbital element distributions for the most numerous single-apparition TNOs do not suggest the existence of a sharp edge for the belt near 50 AU. We also provide refined ephemeris predictions for the poorly observed TNOs.
Planetary and Space Science, 2015
Advances in Space Research, 2015
Meteoritics & Planetary Science, 2014
Journal of Geodynamics, 2009
The monthly variation in the water mass of the semi-enclosed Baltic Sea is about 60 Gt RMS over a... more The monthly variation in the water mass of the semi-enclosed Baltic Sea is about 60 Gt RMS over an area of 390,000textrmkm2390,000 \textrm{km}^2390,000textrmkm2 . The Baltic has a dense network of tide gauges (TGs), and several high-resolution regional hydrodynamic models, making it one of the best-monitored seas for mass variations of this size in the world. We investigate the performance of different GRACE gravity field solutions to recover this oceanic mass variation using in situ measurements of sea-level heights. For GRACE, we use both the standard monthly solutions as well as regional solutions to estimate the total water storage in the Baltic Sea. For the “ground truth”, we use sea-level measurements in the network of tide gauges around the Baltic Sea. For comparison, we have access to data from two hydrodynamic models. The water mass estimated from the constructed sea surfaces is then compared with different GRACE estimates. At present, we ignore the steric anomalies, as they are small in the Baltic Sea. We also discuss the “leakage” between land hydrology and the Baltic Sea in the GRACE estimates of water storage.
We report 8 years of previously unpublished photometric observations of FK Com. The observations ... more We report 8 years of previously unpublished photometric observations of FK Com. The observations have been carried out between 1993 and 2001 with six different telescopes: 60 cm at Mt. Maidanak (Tashkent, Uzbekistan), Phoenix 10, Wolfgang and Amadeus located in Arizona, USA, and 20cm and 60 cm KVA on La Palma, Spain. Observations contain measurements at the following bands: Johnson U, B, V and R, Bessel R, Cousins I and Stromgren b and y. The observations are differential photometry in respect to the primary comparison star HD 117567. NOTE: Table 1 in the paper contains some small misprints in the Julian dates. Also for Wolfgang and Amadeus the number of observations given in Table1 at each band is slightly less than actually given in Table2c and Table2d. This is caused by accidentally using a limiting error of 0.01 in magnitudes when creating Table 1. In Table 2 the limiting error for Wolfgang and Amadeus is 0.02 mag, as mentioned in the paper itself. In Table2a-e 99.0000 means that no observations were available at that time at that band or that the error in the magnitude was larger than 0.02. (5 data files).
Monthly Notices of The Royal Astronomical Society, 2006
We present a statistical orbit computation technique for asteroids with transitional observationa... more We present a statistical orbit computation technique for asteroids with transitional observational data, that is, a moderate number of data points spanning a moderate observational time interval. With the help of local least-squares solutions in the phase space of the orbital elements, we map the volume of variation as a function of one or more of the elements. We sample the resulting volume using a Monte Carlo technique and, with proper weights for the sample orbital elements, characterize the six-dimensional orbital-element probability density function. The volume-of-variation (VOV) technique complements the statistical ranging technique for asteroids with exiguous observational data (short time intervals and/or small numbers of observations) and the least-squares technique for extensive observational data. We show that, asymptotically, results using the new technique agree closely with those from ranging and least squares. We apply the technique to the near-Earth object 2004 HA39, the main-belt object 2004 QR and the transneptunian object 2002 CX224 recently observed at the Nordic Optical Telescope on La Palma, illustrating the potential of the technique in ephemeris prediction. The VOV technique helps us assess the phase transition in orbital-element probability densities, that is, the non-linear collapse of wide orbital-element distributions to narrow localized ones. For the three objects above, the transition takes place for observational time intervals of the order of 10 h, 5 d and 10 months, respectively, emphasizing the significance of the orbital-arc fraction covered by the observations.
Proceedings of The International Astronomical Union, 2007
Canadian Journal of Physics, 2003
We present photometry of snow samples in the backscattering direction, i.e., at very small phase ... more We present photometry of snow samples in the backscattering direction, i.e., at very small phase (light-source - target - observer) angles. Relative brightness measurements are taken to study the backscattering behaviour of snow and ice samples to be able to interpret the opposition effect of icy solar-system surfaces (for example, icy rings and satellites). Preliminary results of three separate experiments are presented, all of which exhibit a similar feature: a backscattering peak is exhibited by snow of different grain types and with different amounts of contamination. The peak grows stronger with increasing contamination.
Advances in Space Research, 2006