What NASA planned in its post-shuttle space projects? Would more non-human space explorers be seen in the near future? After the shuttle fleet, astronomical science projects without human beings on board could come into U.S. space spotlight.

Coinciding with President Barack Obama and shuttle astronauts meet this week, in which President Obama honored the astronauts for the 30-year shuttle program that ended on July 21, NASA has made three significant announcements, a probe of the asteroid Vesta, a look into the dark heart of a galaxy and the imminent launch of a spacecraft headed for Jupiter.

While over $8 billion has been allotted for manned spaceflight in the proposed NASA budget for fiscal year 2012, space science projects without any U.S. human-rated space vehicle have got some $5 billion. However, non-human space vehicles are not in immediate prospect. Through 2020, the smaller Russian Soyuz capsules will be used to get astronauts to the International Space Station, Reuters reported.

Human spaceflights are more expensive than the unmanned explorations or ground-based observatories as they require Earth-like conditions.

Although human spaceflights have gained much attention so far, robotic probes and observatories have been proved to be the biggest leap in unearthing key facts about the cosmos, whether it's roaming around Mars or looking billions of years back in time to understand the origin of the galaxies.

Even during the shuttle era, robotic probes delivered even bigger scientific bangs then the experiments done by human space voyagers. To name a few, the first one would be the "theoretical explosion that gave birth to the universe", a revelation that has been a focus of the Hubble Space Telescope.

The Hubble Space Telescope, which is considered to be the most important astronomical instrument since Galileo looked through a lens, was launched in 1990 for $3.1 billion. While all shuttle missions cost over $1 billion each, the lifetime cost of the Hubble Space Telescope, which has been repaired and upgraded five times by shuttle crews, stands at about $10 billion.

So far, Hubble has been successful to look back in space-time to 400 million years after the Big Bang and revealed some of the first galaxies formed after the first blast. Other successful unmanned discoveries include the microwave remains of the Big Bang, the age of the universe (13.7 billion years), discoveries about comets and asteroid, and the latest one - the evidence of salty liquid water on Mars.

More money to crewed space programs

In order to put more money to crewed space programs, NASA has cut its budget for fiscal year 2012 by more than $2 billion.

The 2010 Obama administration decided to scrap the $10 billion Constellation program that aimed to return U.S. astronauts to the Moon by 2020. John Grunsfeld, deputy director of the Space Telescope Science Institute in Baltimore, which manages Hubble, criticized this decision by Obama administration saying that it's a "poor national management."

Instead of the Constellation program, it's the commercial space taxi services provided by private companies that would be financed by the United States. The commercial space taxi services providers are developing spaceships to carry people and cargo to the space.