Outer Moons of Jupiter
My DLR colleague Stefano Mottola and I perform an observation campaign of the irregular satellites of Jupiter to measure lightcurves for rotation period, spin-axis orientation, and shape determination. For this task, we use the 1.23-m telescope at Calar Alto in southern Spain which allows us to observe the ∼7 largest of Jupiter's outer moons in greater detail.
Paper on Himalia's rotation period:
Pilcher, F., Mottola, S., Denk, T. (2012): Photometric Lightcurve and Rotation Period of Himalia (Jupiter VI). Icarus 219, 741-742. doi:10.1016/j.icarus.2012.03.021.
Paper on Cassini's Jupiter flyby in Dec 2000, including observations of Himalia:
Porco, C.C., 23 colleagues (2003): Cassini Imaging of Jupiter's Atmosphere, Satellites, and Rings. Science 299, no. 5612, 1541-1547. doi:10.1126/science.1079462.
An excerpt of the part describing the Himalia findings can be found here.
Calar-Alto related webpages:
Weather forecast (continuous live data stream)
Current Meteosat weather picture
Calar-Alto webcams (continuous live data stream); the WEST and NORTH views show the 1.23-m telescope
1.23-m telescope timeline 2012, 1st half 2015
Table 2: Physical and astronomical properties of the largest irregular moons of Jupiter
|Moon||Spice ID1||Orbit2||Absolute magnitude
|Best apparent magnitude
Notes for Table 2:
1...SPICE is a commonly-used information system of NASA's Navigation and Ancillary Information Facility (NAIF). It assists engineers in modeling, planning, and executing planetary-exploration missions, and supports observation interpretation for scientists. Each planet and moon obtained a unique SPICE number.
2...The irregular satellites of Jupiter can be subdivided into objects with prograde and objects with retrograde orbits. The moons in the prograde Himalia group share an inclination close to 28°. The retrograde irregulars are more diverse, they orbit Jupiter in three distinct groups at inclinations ranging from 144° to 165°. The naming convention is that all prograde irregular moons of the Himalia group have names ending with an ‘a’, the retrograde moon's names end with an ‘e’. As of end-of-Sep 2012, 7 prograde and 52 retrograde irregular Jovian moons were known; 12 of the retrogrades were in danger of being lost or effectively lost (Jacobson et al. 2012; see also JPL's SSD websites).
3...The absolute magnitude and satellite diameters (except for Themisto) are taken from Rettig et al. (2001). They assume an albedo of 0.04 for all satellites. The axes of Himalia are from our Cassini work, published in Porco et al. (2003). The absolute magnitude is the magnitude (brightness) of an object if located 1 AU away from the sun and observed at 0° phase angle (i.e., the observer virtually sits at the center of the sun in this definition). Smaller numbers indicate brighter objects. The magnitude scale is logarithmic, with an object of 6th mag being 100x darker than a 1st mag object. The conversion from absolute magnitude H to size is given by this formula or this table if the object's albedo is given or reasonably guessed.
4...Best apparent magnitude as seen from Earth of each irregular moon at the 2012/2013 apparition. Smaller numbers again indicate brighter objects. The human eye can spot celestial objects down to ∼6th magnitude.
5...All values are synodic rotation periods. The Himalia value is from our Pilcher et al. (2012) paper. The Lysithea, Sinope, Carme, and Ananke periods are from Luu (1991). They are erroneous by ∼0.3 to ∼3.1 h and will be replaced by more accurate values soon. Rettig et al. (2001) observed Leda over three consecutive nights, but could not extract a rotation period and thus note ∼24 h as a possible value for Leda.
6...The data for the orbital parameters are taken from Scott Sheppard's website.