Near-Earth asteroid flybys for April 2009

Even Deimos only requires 20 kph to break orbit.

March was pretty fun with a couple asteroids flying by within the orbit of the Moon or just a wee bit beyond it, but April doesn't look to be half as interesting. Asteroids are often discovered just a few days before flying by though, so it's still possible that we'll have something newsworthy during the month. Here's what NASA gives us for April:

Object Name	Close Approach Date	Miss Distance (AU)	Miss Distance (LD)	Estimated Diameter*	H (mag)
(2007 YF)	2009-Apr-02	0.0936	36.4	30 m - 66 m	24.8
(2009 FU30)	2009-Apr-02	0.0226	8.8	30 m - 67 m	24.7
(2009 FX10)	2009-Apr-02	0.0378	14.7	36 m - 81 m	24.3
(2004 VC)	2009-Apr-03	0.1319	51.3	480 m - 1.1 km	18.7
(2009 FS4)	2009-Apr-04	0.0351	13.6	25 m - 55 m	25.2
(2006 SX217)	2009-Apr-06	0.1623	63.2	440 m - 970 m	18.9
208617 (2002 EB3)	2009-Apr-10	0.1061	41.3	790 m - 1.8 km	17.6
(2009 FO28)	2009-Apr-10	0.1017	39.6	170 m - 380 m	21.0
(2009 DL46)	2009-Apr-14	0.1301	50.6	130 m - 300 m	21.5
(2007 SQ6)	2009-Apr-14	0.1724	67.1	110 m - 250 m	21.9
(2009 FE)	2009-Apr-15	0.1032	40.2	150 m - 330 m	21.3
(2008 VC)	2009-Apr-19	0.1896	73.8	11 m - 25 m	26.9
(2003 SG170)	2009-Apr-19	0.1484	57.7	770 m - 1.7 km	17.7
(2009 CQ1)	2009-Apr-21	0.1351	52.6	210 m - 480 m	20.5
(2009 FJ30)	2009-Apr-21	0.0223	8.7	88 m - 200 m	22.4
(2009 FP28)	2009-Apr-26	0.1004	39.1	190 m - 420 m	20.8
194386 (2001 VG5)	2009-Apr-26	0.1503	58.5	1.3 km - 2.8 km	16.6
(2009 FU23)	2009-Apr-27	0.1738	67.6	250 m - 570 m	20.1
(2007 WA)	2009-Apr-28	0.0871	33.9	30 m - 68 m	24.7
164207 (2004 GU9)	2009-Apr-28	0.1885	73.4	160 m - 350 m	21.1

The asteroid that flew by us around March 2nd had a magnitude of 11, so you can see that none of these are even comparable.

However!

You can see that most of them are actually fairly large, and in terms of finding a good location for an eventual manned mission to an asteroid we have a nearly limitless number of candidates. There's one in June for example that is quite large and will have a relatively close flyby:

136617 (1994 CC)

2009-Jun-10

0.0168

6.6

780 m - 1.7 km

17.7

8.39

So at closest approach this asteroid will only be 6.6 times the distance from us to the Moon, and if you factor in the fact that there's almost no gravity to worry about when taking off for the mission back to Earth, it's actually a far easier destination to return from. Lifting off from an asteroid like this is more a matter of pushing away than lifting off.

Apparently the most pressing concern for exploring a near-Earth asteroid would be dust kicked up by astronauts on the surface which would then cling due to a combination of static electricity and far too little gravity. Here's an example of an asteroid with a similar size:

Because of its low gravity, Dactyl has an escape velocity of only 0.5 metres per second.

With an escape velocity that low you would still need to be careful not to fall off the surface as a single jump provides six times the force needed to leave the asteroid. Along with the annoyance of dust, it's probably best for NASA to choose as large an asteroid as possible (plus larger ones provide more room to explore), since a manned mission would take a few weeks anyway.