Solar Ephemerides Research Articles

The Greenwich Photo-heliographic Results (1874 – 1976): Initial Corrections to the Printed Publications

A new sunspot and faculae digital dataset for the interval 1874 – 1955 has been prepared under the auspices of the NOAA National Geophysical Data Center (NGDC). This digital dataset contains measurements of the positions and areas of both sunspots and faculae published initially by the Royal Observatory, Greenwich, and subsequently by the Royal Greenwich Observatory (RGO), under the title Greenwich Photo-heliographic Results (GPR), 1874 – 1976. Quality control (QC) procedures based on logical consistency have been used to identify the more obvious errors in the RGO publications. Typical examples of identifiable errors are North versus South errors in specifying heliographic latitude, errors in specifying heliographic (Carrington) longitude, errors in the dates and times, errors in sunspot group numbers, arithmetic errors in the summation process, and the occasional omission of solar ephemerides. Although the number of errors in the RGO publications is remarkably small, an initial table of necessary corrections is provided for the interval 1874 – 1917. Moreover, as noted in the preceding companion papers, the existence of two independently prepared digital datasets, which both contain information on sunspot positions and areas, makes it possible to outline a preliminary strategy for the development of an even more accurate digital dataset. Further work is in progress to generate an extremely reliable sunspot digital dataset, based on the long programme of solar observations supported first by the Royal Observatory, Greenwich, and then by the Royal Greenwich Observatory.

The Greenwich Photo-heliographic Results (1874 – 1976): Procedures for Checking and Correcting the Sunspot Digital Datasets

Attention is drawn to the existence of errors in the original digital dataset containing sunspot data extracted from certain sections of the printed Greenwich Photo-heliographic Results (GPR) 1874 – 1976. Calculating the polar coordinates from the heliographic coordinates and comparing them with the recorded polar coordinates reveals that there are both isolated and systematic errors in the original sunspot digital dataset, particularly during the early years (1874 – 1914). It should be noted that most of these errors are present in the compiled sunspot digital dataset and not in the original printed copies of the Greenwich Photo-heliographic Results. Surprisingly, many of the errors in the digitised positions of sunspot groups are apparently in the measured polar coordinates, not the derived heliographic coordinates. The mathematical equations that are used to convert between heliographic and polar coordinate systems are formulated and then used to calculate revised (digitised) polar coordinates for sunspot groups, on the assumption that the heliographic coordinates of every sunspot group are correct. The additional complication of requiring accurate solar ephemerides in order to solve the mathematical equations is discussed in detail. It is shown that the isolated and systematic errors, which are prevalent in the sunspot digital dataset during the early years, disappear if revised polar coordinates are used instead. A comprehensive procedure for checking the original sunspot digital dataset is formulated in an Appendix.

Monddaten aus dem Archiv von Illahun: Chronologie des Mittleren Reiches

Abstract Last/first sightings of the lunar crescent and new moon epochs between 2000 BC and 2000 AD were calculated using modern up-to-date lunar and solar ephemerides for different locations in Egypt and for Babylon. All results of these calculations are available online. The lunar data from the archive of Illahun are reanalysed and the uncertainties of the data reduction and possible absolute chronological assessments are discussed. The data can be fit best when a reign length of 30 years is allowed for pharaoh Senwosret III, which is in accordance with the given number for this king in the Turin papyrus. The lunar data do not support a low chronology of the Middle Kingdom. Two temporal assignments are possible in combination with the recorded date of a heliacal rising of Sirius on either IIII Peret 16 or 17 in the surrounding of Memphis. The best fit (82.5% reproduced correctly) can be obtained with an assumed beginning of the day with dawn and year 1 of Senwosret III equalling 1872 BC and year 1 of Amenemhet III in 1842 BC respectively. In this case the correct Sirius date of year 7 Senwosret III in 1866 BC must have been IIII Peret 17 in order to match with the lunar data. The second possible fit (72.5% correct) is obtained with an assumed beginning of the day with sunrise and year 1 of Senwosret III equalling 1883 BC and year 1 of Amenemhet III in 1853 BC respectively. The correct Sirius date would be IIII Peret 16 in 1877 BC.

Does swarming cause honey bees to update their solar ephemerides?

Spatial orientation in the social insects offers several examples of specialized learning mechanisms that underlie complex learning tasks. Here we study one of these systems: the processes by which honey bees update, or fail to update, their memories of the sun's daily pattern of movement (the solar ephemeris function) in relation to the landscape. Specifically, we ask whether bees that have initially learned the solar ephemeris function relative to a conspicuous treeline at their natal site can later realign the ephemeris to a differently oriented treeline. We first confirm and clarify an earlier finding that bees transplanted passively (by being carried) do not re-learn the solar ephemeris in relation to the new treeline. When they cannot detect the sun directly, as on overcast days, these transplanted bees use a solar ephemeris function appropriate for their natal site, despite days or weeks of experience at the new site. We then ask whether bees put through a swarming process as they are transplanted are induced to re-learn the solar ephemeris function at the new site, as swarming is a natural process wherein bees transplant themselves. Most of the swarmed bees failed to re-learn, even though they did extensive learning flights (in comparison with those of non-swarmed controls) as they first emerged from the hive at the new site. We hypothesize that the bees' representation of the solar ephemeris function is stored in an encapsulated cognitive module in which the ephemeris is inextricably linked to the reference landscape in which it was learned.

Attitude determination studies for the Earth Observation System AM1 (EOS-AM1) mission

The application of Kalman filter-based attitude determination, with simultaneous gyro bias estimation, to the Earth Observation System (EOS) AMI mission with stellar measurements is analyzed. The study examines the predictive capability of covariance analysis as compared with Monte Carlo analysis, showing that thrice the square root of the Kalman filter covariance matrix diagonal is a reasonable prediction for the 99.7% Monte Carlo results, but not of worst-case performance. The study also establishes further insight into the sensitivity of EOS-AMI attitude determination performance to simulated stellar-lunar geometries by comparing Monte Carlo performance predictions using a statistically generated star field (including statistical lunar blockage gaps) with those using a physical model (real star field and lunar and solar ephemerides). This study further demonstrates that, with EOS-AMI parameters, the performance is driven by the sensor noise rather than the gaps in the star field and confirms these conclusions by Monte Carlo assessments of the orbits with short and long star gaps.

The effect of various solar ephemerides on equator and equinox solutions from observations of the Sun with the reversible transit circle at Cape observatory from 1907 to 1959

Observations of the Sun were made with the Cape reversible transit circle from 1907 to 1959. We have made least squares solutions for six unknowns viz., equator and equinox corrections and corrections to earth orbital parameters including the ephemeris mean longitude of the Sun, the mean obliquity of the ecliptic, the mean longitude of perihelion, and the mean eccentricity of the earth's orbit based on Newcomb's, DE102, and DE200 Ephemerides for each of six catalogs of observations made during that period. The six unknowns are also determined simultaneously for the six catalogs taken together. The six catalogs are absolute, in that methods of observation and reduction were adopted in such a way as to produce a system of results not closely dependent on the adopted system of assumed clock and azimuth star positions.