Sourcebook on the Space Sciences

altitude angle antennas appear astronomical astronomical unit atmosphere atoms average axis body brightness centimeter charged particles chromosphere clouds comet craters decrease determined diameter direction distance Doppler Earth electrical electron density electron volts elliptical emission energy equation flares frequency galactic galaxies geomagnetic gravitational heat helium hence hydrogen increase indicated infrared ionization ionosphere ions Jupiter kilometers launch light lines liquid lunar lunar surface magnetic field main sequence Mars mass maximum measurements Mercury meteorites meteoroid meters micrometeoroid miles million module molecules Moon motion observed orbital period orbital plane oxygen parsecs percent photosphere planet plasma possible pounds pressure produced propellant protons radar radiation radio waves radius region relatively result rocket vehicle rotation satellite sidereal period signal solar sounding rockets space spacecraft specific impulse spectra spectrum stars sunspot tektites temperature terrestrial thrust tion trajectory ultraviolet velocity Venus wavelength