1999 Stellar Occultations

Amanda S. Bosh, Lowell Observatory

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Event Times and Occultation Paths from Specific Observatories

Event epsf plots gif plots Im Mid Em B OER B OER A IER A OER F

Saturn, 1999 Dec. 03 UT
All listed locations epsf plot gif plot
ESO epsf plot gif plot 4:03 (16.8) 4:31 5:04 (16.7) 5:30 (-0.5) 5:40 ( 1.6) 6:02 ( 6.2) 6:31 (10.9) 6:37 (11.5)
IRTF epsf plot gif plot 3:58 (16.5) 4:37 5:20 (16.7) 6:20 (11.0) 6:27 (11.9) 6:46 (14.1) 6:50 (14.5)
Kitt Peak epsf plot gif plot 3:54 (16.7) 4:33 5:16 (16.7) 6:16 (11.0) 6:22 (11.9) 6:41 (14.1) 6:46 (14.5)
Lick epsf plot gif plot 3:54 (16.7) 4:34 5:17 (16.7) 6:18 (11.4) 6:24 (12.4) 6:43 (14.4) 6:47 (14.8)
Lowell epsf plot gif plot 3:54 (16.7) 4:33 5:16 (16.7) 6:16 (11.1) 6:23 (12.1) 6:44 (14.3) 6:46 (14.6)
San Pedro Martir epsf plot gif plot 3:55 (16.7) 4:34 5:16 (16.7) 6:16 (10.9) 6:23 (12.1) 6:42 (14.3) 6:46 (14.5)
WIRO epsf plot gif plot 3:53 (16.7) 4:32 5:16 (16.7) 6:16 (11.4) 6:23 (12.4) 6:42 (14.4) 6:46 (14.8)

Notes to Saturn table

Saturn table entries. Times and appropriate velocities are listed for relevant events. Only ESO has a B outer edge immersion listed; for all other stations B OER im occurs while the star is still behind the planet. Longer column titles:
  • epsf plot
  • gif plot
  • Immersion UT (sky-plane velocity, km/sec)
  • Close approach UT
  • Emersion UT (sky-plane velocity, km/sec)
  • B ring outer edge immersion (ring-plane velocity, km/sec)
  • B ring outer edge emersion (ring-plane velocity, km/sec)
  • A ring inner edge emersion (ring-plane velocity, km/sec)
  • A ring outer edge emersion (ring-plane velocity, km/sec)
  • F ring emersion (ring-plane velocity, km/sec)

    Note that planet emersion (except for ESO) will be difficult to observe because the B ring will be between the star and the planet.

    Ring radii used were: F (140223), A OER (136780), A IER (122170), B OER (117580); all in km. Rings were modeled as circular; no eccentricities or inclinations included. Star position RA = 02 40 15.7118, Dec = +12 53 53.290 (J2000) from ACT. This catalog includes proper motion calculated from the Tycho and AC2000 catalogs. Proper motion has been applied to the above position, for epoch J2000. Using a DE406 ephemeris for the Saturn barycenter and Earth center. Uncertainties arise from lack of correction for barycenter offset (Saturn).

    Saturn radius at 10 microbar taken to be 60880. km. Flattening of 0.098. These parameters are used for the plots and atmosphere time predictions. Gravitational focussing not included.

    Sky-plane velocity is true shadow velocity, not velocity perpendicular to the limb. Ring-plane velocity really is what it sounds like.

    A map of the region around this star is available. To make other maps, go here.

    The arrangement of satellites at midtime (cross is occ. star) is available here or from Mark Showalter's Rings Node On-line Tools page

    Event ps/epsf plots gif plots Immersion UT Im velocity (km/sec) Emersion UT Em velocity (km/sec) Close-approach UT

    Jupiter, 1999 Oct. 10 UT
    select locations ps plot gif plot
    auroral oval ps plot gif plot caption
    Apache Point epsf plot gif plot 6:42:06 15.6 7:31:25 15.6 7:06:32
    ESO epsf plot gif plot 6:24:10 15.6 7:46:59 15.6 7:05:21
    Geocentric epsf plot gif plot 6:33:04 15.2 7:38:45 15.3 7:05:45
    IRTF epsf plot gif plot 6:48:41 15.4 7:33:59 15.5 7:11:06
    Kitt Peak epsf plot gif plot 6:43:06 15.6 7:31:36 15.6 7:07:07
    Lick epsf plot gif plot 6:46:29 15.5 7:29:11 15.6 7:07:36
    Lowell epsf plot gif plot 6:43:51 15.6 7:30:27 15.6 7:06:55
    Mont Megantic, Quebec epsf plot gif plot 6:39:13 15.5 7:27:06 15.5 7:02:56
    VLT epsf plot gif plot 6:24:34 15.6 7:46:04 15.6 7:05:05
    WIRO epsf plot gif plot 6:44:14 15.6 7:28:22 15.6 7:06:04
    Yerkes epsf plot gif plot 6:41:17 15.6 7:28:09 15.6 7:04:30

    Notes to Jupiter table

    Auroral oval plot by Leslie Young (BU).

    Jupiter plots and atmosphere times calculated for an equatorial radius of 71880-84 km = 71796 km. Flattening of 0.0600028 included in all calculations. The 84 km is subtracted to account for GR bending and refraction. All times are UTC. Effects included in prediction include stellar proper motion, offset of Jupiter from its barycenter, oblateness of Jupiter, topocentric location of observer. Ephemeris used for Jupiter barycenter and Earth center is DE406. Ephemeris used for galilean satellites (to calculate barycenter offset) is DE405. All ephemerides are from JPL/Horizons.

    Sky-plane velocity is true shadow velocity, not velocity perpendicular to the limb.

    Timing uncertainties for Jupiter occultation

    Star position and proper motion

    The quoted position error in the Hipparcos catalog is (7.7, 6.4) mas -> 10 mas.

    The error in the proper motion is (1.94, 2.42) mas/yr at 1991.25. 3.10 mas/yr times 8.5 yr = 26 mas

    The resulting uncertainty in position at epoch is 28 mas. To translate this into a timing uncertainty, convert to km at Jupiter and divide by sky-plane velocity: 0.028 arcsec x 2900 km/arcsec / (15.5 km/sec) = 5 sec.

    Timing uncertainty due to star position uncertainty: 5 seconds

    Microbar level

    "Hubbard" Source 1971 beta Sco occultation (AJ 77, 65). Equatorial radius = 71880 +/- 30 km, polar radius = 67567 +/- 72.

    "Lindal" Source JGR 86, 8721, referenced from 100 mbar isobaric surface. Equatorial radius = 71797 km, polar radius = 67152 km.

    The largest timing difference due to this change is on the order of 100 seconds. [All the times in the table above use the "Hubbard" radius, adjusted for GR bending and refraction.]

    Timing uncertainty due to uncertainty in microbar level in Jovian atmosphere: 100 seconds

    Offset between reality and DE406

    Unknown.

    Overall timing uncertainty

    About 100 seconds. Pad as you feel necessary/able. I'm going to try for 3 times this, or about 5 minutes.

    Observation Duration

    Calculated by Leslie Young. To get to the 1% level on both upper and lower baselines, Leslie calculates that you will need to integrate for 1 min. (before on immersion/after on emersion), and 13 min. (after on immersion/before on emersion). The longer time is for the lower baseline. These times are for a vperp of 4 km/sec. Some sites (southern hemisphere) will have larger vperps and therefore shorter times.

    Event ps/epsf plots gif plots Immersion UT Im velocity (km/sec) Emersion UT Em velocity (km/sec) Close-approach UT

    Titan, 1999 Oct. 20 UT
    Selected sites epsf plot gif plot
    IRTF epsf plot gif plot 12:15:47 20 12:20:10 21
    Lowell epsf plot gif plot 12:12:57 22 12:17:34 22
    Lick epsf plot gif plot 12:13:27 22 12:18:01 22
    KPNO epsf plot gif plot 12:12:55 22 12:17:32 22

    Notes to Titan table

    Using a radius of 3000 km for Titan's extended atmosphere. Assumed to be spherical. DE406 ephemeris for Titan center and Earth center. Star position measured by Ron Stone (USNO), uncertainty about 50 mas. For comparison, the typical uncertainty in the USNO-A2.0 catalog is about 0.25 arcsec, which translates into 1497 km at Titan, or 75 seconds of time.

    Change Log

    991127. Added prediction times for Saturn, rearranged page.

    991121. Added estimated date for publishing Saturn event times.

    991017. Added immersion/emersion times and velocities for Titan event.

    991008. 14:50 MST. Updated Jupiter predicted times. Added discussion on sources of timing uncertainties. Added Leslie's calculations of event duration.

    991005. Added Titan occultation plot.

    991004. Added table notes.

    990922. Added plots for Saturn event in December 1999. Uses star position from ACT, and barycentric DE406 ephemeris for Saturn.

    990330. Added plot of Jupiter's auroral oval with occultation immersion points indicated. Calculated by Leslie Young, auroral coordinates supplied by John Clarke.

    990324. Thanks to Pierre Drossart and Bruno Sicardy for pointing out an error in ring orientation. This was due to an error in the code when it decided which section of the ring was behind vs. in front of the planet. This has been fixed, and new plots have been installed in the plot matrix.

    Send questions and feedback to amanda@lowell.edu