Asteroid 2017 DQ15

Asteroid 2017 DQ15 is a NEO (Apollo) displayed in the list of objects with a comet-like orbit maintained by Y. Fernandez.

Orbital Elements at Epoch 2458000.5 (2017-Sep-04.0) TDB
Reference: JPL 7 (heliocentric ecliptic J2000)

Element Value Uncertainty (1-sigma)   Units  e .7272164269790051 1.279e-05 a 2.823784780342436 0.00011852 au q .7702821018241148 3.8782e-06 au i 20.18557131636563 0.00017551 deg node 272.8777420846461 0.00046785 deg peri 350.4179039106148 0.00040687 deg M 22.44168793940112 0.0013623 deg tp 2457892.456452631231 (2017-May-18.95645263) 0.00026204 JED period 1733.18857109974 4.75 0.10912 0.0002988 d yr n .207709654911683 1.3077e-05 deg/d Q 4.877287458860757 0.00020471 au

Orbit Determination Parameters    # obs. used (total)      43      data-arc span      187 days      first obs. used      2017-02-10      last obs. used      2017-08-16      planetary ephem.      DE431      SB-pert. ephem.      SB431-N16      condition code      5      fit RMS      .50315      data source      ORB      producer      Otto Matic      solution date      2017-Aug-17 06:19:02   Additional Information  Earth MOID = .22774 au   Jupiter MOID = .339108 au   T_jup = 2.792

Based on the nominal orbital parameters and uncertainty, I generated 100 clones with an R script and then I used the Mercury6 simulator by J.E. Chambers to investigate what happened in the last 10^8 days.

Mercury6 simulator: configuration

More about the program "A Hybrid Symplectic Integrator that Permits Close Encounters between Massive Bodies'' can be found here.

Main integration parameters:

   Algorithm: Bulirsch-Stoer (conservative systems)

   Integration start epoch:         2458000.5000000 days
   Integration stop  epoch:        -10^8 days
   Output interval:                     100.000 days
   Output precision:                   medium
   Initial timestep:                      0.100 days
   Accuracy parameter:             1.0000E-12
   Ejection distance:                  1.0000E+02 AU

Simulation results

As seen above, the "ejection distance" used to claim that an asteroid has arrived from the outskirts of the solar system is 100 AU.

The simulation shows that there is a good likelyhood that the asteroid has a cometary origin:

• 47 out of 100 clones arrived from a distance greater than 100 AU in the last 10^8 days
• 4 out of 100 clones would have "collided" with the sun 

The most recent arrival time was about 7906 B.C.

The mean arrival time was about 139274 B.C.

The less recent arrival time was about 268318 B.C.

The arrival time distribution of the 47 clones that were likely to be comets is shown below:

Kind Regards,

Alessandro Odasso

Near-Earth Asteroid Delta-V

JPL maintains an interesting list: Near-Earth Asteroid Delta-V for Spacecraft Rendezvous

Let's display how Delta-V depends on perihelium q=a*(1-e)

(Graphs are done with  R package and the related ggplot function)

Neo with q <=1
Delta-V (km/s) vs q (AU)

The red line is a very rough approximation for the lower boundary of Delta-V (km/s) as a function of q (AU):

delta-v = -7.3q + 11.4 when q<=1

Neo with q> 1
Delta-V (km/s) vs q (AU)

The red line is a very rough approximation for the lower boundary of Delta-V (km/s) as a function of q (AU):

delta-v = 4.6q - 0.5 when q>1

Three "bands" for Delta-V
As stated in the JPL page, for comparison, Delta-V for transferring from Low Earth Orbit to rendezvous with Moon and Mars:

• Moon: 6.0 km/s
• Mars: 6.3 km/s

Thus, we can graphically display three bands for Delta-V. I call them as follows:
1) moon-like (Delta-V <= 6.0 km/s)
2) mars-like (Delta-V <= 6.3 km/s)
3) beyond-mars (Delta-V > 6.3 km/s)

Neo with q <=1
Delta-V (km/s) vs q (AU)

Neo with q > 1

Delta-V (km/s) vs q (AU)

We can look at the neo distribution in every Delta-V band:

Neo with q <=1

Neo with q >1

Ultra-low Delta-V Neo

I often read that these neo are considered as a particular interesting target for   spacecraft rendezvous missions because very little energy is needed to reach them.

This is a graphical display for neo with Delta-V <= 4.5 km/s:

These ultra low Delta-V neo are just a tiny fraction of the neo population.
This is their proportion:

As known, one of the problems with these neo is that it is very difficult to find relative bright (and thus big) asteroids.

The graph below shows all the ultra low Delta-V asteroids with H (mag) <= 23 showing that only three neo of this group have H (mag) <= 22. They are:

Designation	Delta-V (km/s)	H (mag)
2011 CG2	4.112	21.5
2001 US16	4.428	20.2
2002 NV16	4.460	21.4

(1999 RQ36) Bennu and ("similar?") Neo

Delta-V for Bennu: 5.087 km/s
H (mag) = 20.9

See also:
http://en.wikipedia.org/wiki/101955_Bennu
http://astro.mff.cuni.cz/davok/papers/bennu_osiris_maps2015.pdf

If we give a look at asteroids having Delta-V and H at least comparable (or better) than those of asteroid Bennu, target of the OSIRIS-REx mission, we can find a few other ones.
Bennu is shown at the top-left corner of the image.

Of course, Delta-V is not the only parameter used to decide whether an asteroid is a good candidate for a sample return mission (physical characteristics, a well known orbit and an appropriate rendezvous time are certainly other fundamental aspects!). 

Once said this, I would be interested to know if some of the other asteroids shown here are candidates for similar missions.
In fact, I found an interesting link showing the earth-centric orbit view of many of these asteroids

 

Kind Regards,
Alessandro Odasso