# Comet 2012 S1 (ISON) Geocentric Distance

### Real-time Distance Calculator

 Local Time:The current local time. Universal Time:Standardized time calculated by the rotation of the Earth. Julian Day:Number of days since the year 4712 B.C. Earth-Comet Distance:The current distance from Earth to comet. 1 A.U. (Astronomical Unit) is equal to approx. 93 million miles. Sun-Comet Distance:The current distance from the Sun to the comet. 1 A.U. (Astronomical Unit) is equal to approx. 93 million miles. Comet Velocity:The orbital velocity of the comet estimated by velocity of escape equation and radius vector. Light Time:The time it takes for reflected light to travel from the comet to Earth. Calculation Time:The time required for the system to perform the iterations and display the distance. Although this time is not factored into the equations it will yield a small error in real-time distance. Comet ISON Calculator Page Notes History and Construction The calculator page was designed and built by Horace Dale, Jason Boss, and Scott Meves. The original template was constructed for calculating the Earth-Mars geocentric distance in real time by Horace and Scott back in 2003 for the close approach of Mars in August of that year. Instead of incorporating standard orbital elements (which will change over time) they used the VSOP87 algorithm so updates are needed less frequently. The Mars calculator has been running great ever since. This comet calculator required only few small modifications to the Mars code and should remain accurate enough to keep everyone entertained when Comet ISON is obscured by cloudy conditions. This calculator runs based on the time from your computer, this means, if you have permission to change your system time, you can run the calculator forward or backward to find certain conditions. Some Interesting Things to Look For! The comet will continue to accelerate on its way to perihelion (its closest distance from the sun), which occurs on Nov 28, 2013. In January 2013, the comet was traveling at a little more than 11 miles/second. Watch as the comet velocity increases more rapidly as it approaches perihelion. The comet will reach a maximum velocity of more than 230 miles/second (370 km/sec) as it goes around the sun in November 2013! There are a few dates when the Earth-Comet distance will change font color. Our calculator shows a blue colored font when the Earth-Comet distance is decreasing (or moving closer) and a red font when the distance is increasing (moving away from Earth). This happens because of the relative motions of Earth and the comet around the Sun. The dates to look for are: 8-9 February, 2013 the numbers change from blue to red 12 May, 2013 the numbers change again from red to blue 21 November, 2013 the numbers change from blue to red 28 November, 2013 perihelion, numbers change from red to blue 23 December, 2013 numbers change from blue to red. This will also be the closest to Earth at about 0.4 AU. COMET ISON UPDATE (12/3/2013) All of the data from various orbiting spacecraft that have been watching ISON intently since its close encounter with the sun on November 28, 2013, have been disappointing to say the least. The comet has essentially been disintegrated by the suns intense heat and gravity with only a few small remnants remaining. While the remnants will not be quite as impressive as the intact comet could have been, it may be worthy as a telescopic challenge. As of now the remnants are predicted to have a magnitude of about 8 at the closest approach to earth, meaning not visible to the naked eye. This is the uncertainty of comets! As a tribute to ISON and its remains, we will leave the calculator up and running until the first of the year 2014.