# Is 2012 TC4 part of the Near-Earth Object Human Space Flight Accessible Targets Study?

This nifty answer describes and provides links to the data of the recovery of near earth object 2012 TC4, and the answer also shows the first actual image of the body for this pass. At apparent magnitude +27 (at about 52 million km) it may be the faintest asteroid to have been imaged to date. It's worth visiting that answer first before reading on here.

This comment points out that 2012 TC4 appears on the Goldstone Asteroid Schedule, a list of upcoming planned observations of asteroids by antennas at the Deep Space Network. Here are the entries for 2012 TC4 in the Upcoming Observations and Past Observations tables:

Upcoming Goldstone Observations
DATES           TARGET    H     Notes:
2017 Oct  9-14  2012 TC4  26.7  Close approach = 7.9 Earth radii on Oct. 12. NHATS

Past Goldstone Observations
DATES           TARGET          Notes:
2012 Oct        2012 TC4        Echoes not detected. Likely equipment issues.


I noticed that the 2012 TC4 observation is labeled as a NHATS, or Near-Earth Object Human Space Flight Accessible Targets Study. I tried to find it in the DATA TABLE of NHATS objects but I don't find it there.

Question: Is one of these more up-to-date than the other? Is 2012 TC4 part of the Near-Earth Object Human Space Flight Accessible Targets Study? What does it really mean if 2012 TC4 is or is not part of NHATS anyway?

• Does anyone know what the H of 26.7 listed for the 2017 observation means? – uhoh Aug 12 '17 at 22:52

It is an NHATS object. I found it on there but first I had to select 'Use Unconstrained Settings'. The default view restricts on some parameters. DeltaV is over 10 km/s.

On question over the Goldstone planning info, H=26.7 is the absolute magnitude of the object. This relates to the size and reflectivity (albedo) of the object itself and is not specific to the 2017 apparition. Suggests size is in the range of 9 to 30 meters.

The table can be found at http://www.minorplanetcenter.net/iau/lists/Sizes.html and a subset of the table is shown below.

The line bracket by arrows applies to H=26.5. There are three columns of diameters for three assumed albedos of 0.5, 0.25 and 0.05, and the units are km for H(a), meters for H(b) which applies here, and millimeters for H(c). This is because fifteen magnitudes represents a factor of $10^6$ in brightness or area, which would be a factor of $10^3$ in diameter.

                  Albedos
H(a)   0.50    0.25    0.05    H(b)  H(c)

-2.0    4700 -  6700 - 14900    13.0  28.0

0.0    1900 -  2600 -  5900    15.0  30.0

5.0     190 -   260 -   590    20.0  35.0

0.0      19 -    25 -    60    25.0  40.0
10.5      15 -    20 -    50    25.5  40.5
11.0      12 -    17 -    37    26.0  41.0
-> 11.5       9 -    13 -    30    26.5  41.5 <- this line
12.0       7 -    11 -    24    27.0  42.0
12.5       6 -     8 -    19    27.5  42.5
13.0       5 -     7 -    15    28.0  43.0
13.5       4 -     5 -    12    28.5  43.5
14.0       3 -     4 -     9    29.0  44.0
14.5       2 -     3 -     7    29.5  44.5
15.0       2 -     3 -     6    30.0  45.0

17.5       1 -     1 -     2    32.5  47.5

• Great answer, thank you for tracking this down! I've added a little bit of supporting information so that the answer stands on its own in case the links change in the future. – uhoh Aug 13 '17 at 12:59