helio {astrolibR} R Documentation

## Compute (low-precision) heliocentric coordinates for the planets

### Description

Compute (low-precision) heliocentric coordinates for the planets

### Usage

```helio(jd, list1, radian=FALSE)
```

### Arguments

 `jd` Julian date, scalar or vector `list1` List of planets array. May be a single number. 1 = merc, 2 = venus, ... 9 = pluto `radian` If =TRUE, then the output longitude and latitude are given in radians. If =FALSE, the output are in degrees. (default=FALSE)

### Details

The mean orbital elements for epoch J2000 are used. These are derived from a 250 yr least squares fit of the DE 200 planetary ephemeris to a Keplerian orbit where each element is allowed to vary linearly with time. For dates between 1800 and 2050, this solution fits the terrestrial planet orbits to ~25" or better, but achieves only ~600" precision for Saturn.

These output arrays are dimensioned Nplanet x Ndate, where Nplanet is the number of elements of list1, and Ndate is the number of elements of Jjd.

Use planet_coords (which calls helio) to get celestial (RA, Dec) coordinates of the planets

### Value

 `hrad` array of heliocentric radii, in Astronomical Units `hlong` array of heliocentric (ecliptic) longitudes, in degrees or radians `hlat` array of heliocentric latitudes, in degrees or radians

### Author(s)

R. Sterner 1986 and W. Landsman 2000

R adaptation by Arnab Chakraborty June 2013

`cirrange`

### Examples

```# (1) Find the current heliocentric positions of all the planets

jd_today <- 2456877.5
helio(jd_today,seq(1,9))

# (2) Find heliocentric position of Mars on August 23, 2000
# Result: hrad = 1.6407 AU hlong = 124.3197 hlat = 1.7853
# For comparison, the JPL ephemeris gives hrad = 1.6407 AU hlong = 124.2985 hlat = 1.7845
helio(2451779.5,4)
```

[Package astrolibR version 0.1 Index]