by  David Seidel of the JPL Education Office

• For every day over the last decade there has been one to three Americans living and working in space on the International Space Station, 4,000 straight days as of Sunday, October 16, 2011.
• For every day for the next decade there will be one to three Americans living and working in space on the International Space Station.
• There are four space vehicles capable of visiting ISS (Soyuz, Progress, ESA’s Automated Transfer Vehicle and Japan’s H-2 Transfer Vehicle).
• Several private companies are vying for work to deliver cargo and, eventually crew, to and from ISS. SpaceX may fly its Dragon spacecraft to rendezvous and dock with ISS before the end of this year. Orbital Science’s Cygnus spacecraft may have a test flight before the end of the year as well.
• At this moment there are robotic spacecraft in orbit around eight different planetary bodies (Sun, Mercury, Venus, Earth, Moon, Mars, Saturn and Vesta). (Note that the ESA’s Venus Express is not a NASA mission but there is some NASA support.) Three additional spacecraft (Voyagers and New Horizons) are on solar system escape trajectories.
• There is a mission on the way to orbit Jupiter (Juno) and the Grail twins are on the way to the Moon.
• There are three operational spacecraft in orbit around Mars and an operating rover on the surface (Opportunity).
• NASA’s Science Mission Directorate lists 63 operational spacecraft and 36 space missions under development.
• JPL has 39 missions and instruments in some stage of the mission life-cycle. (These are either already in flight or being prepared; it does not include future competitions or hoped-for missions.)