A communication coverage gap exists for Deep Space Network (DSN) antennas. This communication coverage gap is on the southern hemisphere, centered at approximate latitude of -47deg and longitude of -45deg. The area of this communication gap varies depending on the altitude from the Earth s surface. There are no current planetary space missions that fall within the DSN communication gap because planetary bodies in the Solar system lie near the ecliptic plane. However, some asteroids orbits are not confined to the ecliptic plane. In recent years, Potentially Hazardous Asteroids (PHAs) have passed within 100,000 km of the Earth. NASA s future space exploration goals include a manned mission to asteroids. It is important to ensure reliable and redundant communication coverage/capabilities for manned space missions to dangerous asteroids that make a sequence of close Earth encounters. In this paper, we will describe simulations performed to determine whether near-Earth objects (NEO) that have been classified as PHAs fall within the DSN communication coverage gap. In the study, we reviewed literature for a number of PHAs, generated binary ephemeris for selected PHAs using JPL s HORIZONS tool, and created their trajectories using Satellite Took Kit (STK). The results show that some of the PHAs fall within DSN communication coverage gap. This paper presents the simulation results and our analyse

Bhasin, Kul

Bittner, David

Gati, Frank

Kegege, Obadiah

NASA Technical Reports Server

 
 
2012 NSBE Aerospace Systems Conference,  Los Angeles,  CA,  February 1-4, 2012. 
 
 
Assessment of DSN Communication Coverage for Space 
Missions to Potentially Hazardous Asteroids 
 
Obadiah Kegege, David Bittner, Frank Gati, Kul Bhasin  
NASA Glenn Research Center 
Cleveland, OH, USA 
obadiah.o.kegege@nasa.gov, david.m.bittner@nasa.gov, frank.gati@nasa.gov, kul.b.bhasin@nasa.gov 
 
Abstract - A communication coverage gap exists for Deep 
Space Network (DSN) antennas. This communication 
coverage gap is on the southern hemisphere, centered at 
approximate latitude of –47° and longitude of –45°. The 
area of this communication gap varies depending on the 
altitude from the Earth’s surface. There are no current 
planetary space missions that fall within the DSN 
communication gap because planetary bodies in the Solar 
system lie near the ecliptic plane. However, some 
asteroids’ orbits are not confined to the ecliptic plane. In 
recent years, Potentially Hazardous Asteroids (PHAs) have 
passed within 100,000 km of the Earth. NASA’s future 
space exploration goals include a manned mission to 
asteroids.  It is important to ensure reliable and redundant 
communication coverage/capabilities for manned space 
missions to dangerous asteroids that make a sequence of 
close Earth encounters. In this paper, we will describe 
simulations performed to determine whether near-Earth 
objects (NEO) that have been classified as PHAs fall 
within the DSN communication coverage gap. In the study, 
we reviewed literature for a number of PHAs, generated 
binary ephemeris for selected PHAs using JPL’s 
HORIZONS tool, and created their trajectories using 
Satellite Took Kit (STK). The results show that some of the 
PHAs fall within DSN communication coverage gap. This 
paper presents the simulation results and our analyses. 
Keywords: DSN Communication gap, Deep Space 
Network, PHA simulation, Asteroids. 
1 Introduction 
  In our recent work [1], we modeled the communication 
coverage gap within DSN and presented both 2D and 3D 
communication coverage profiles showing the location, 
size, and shape of the DSN communication coverage gap 
projected in space at various deep space altitudes. As the 
Earth rotates, the center of this DSN gap is rotating at 
approximate latitude of –47° and longitude of –45° (Figure 
3 and 4) and stretches in space depending on the altitude 
from the Earth’s surface [1]. There are no current planetary 
space missions that fall within the DSN communication gap 
because planetary bodies in the Solar system lie near the 
ecliptic plane. As illustrated in Figure 1 with the example of 
asteroid 2004 QY2, some asteroids’ orbits are not confined 
to the ecliptic plane. In recent years, PHAs have passed 
within 100,000 km of the Earth. On March 2, 2009, the 
Apollo asteroid named 2009 DD45 (approximately 35 m in 
diameter) passed about 72,000 km above the Earth’s 
surface, approximately twice the height of a geostationary 
communications satellite. Also, on March 18, 2004, a 30-m 
Aten asteroid identified as 2004 FH, passed about 43,000 
km above the Earth’s surface, about 0.1 of the distance to 
the Moon.  
 
 
Figure 1. An artistic illustration of DSN supporting 
communication for a manned asteroid mission 
 NASA’s future space exploration goals include both 
robotic and manned missions to asteroids. Asteroids with an 
Earth Minimum Orbit Intersection Distance (MOID) of 0.05 
AU (7,480,000 km) or less and an absolute magnitude (H) 
of 22.0 or less are considered Potentially Hazardous 
Asteroids (PHAs) [2]. A manned mission to an asteroid (as 
depicted in Figure 1) would require redundant 
Three DSN 
locations can 
continuously 
track a deep 
space spacecraft 
as the Earth 
rotates.  
 
https://ntrs.nasa.gov/search.jsp?R=20120004034 2019-08-30T19:49:45+00:00Z
 2 
 
communication coverage at all times. This paper describes 
simulations performed to determine whether PHAs fall 
within the present DSN communication coverage and 
evaluate the capability of the current DSN to support an 
asteroid mission. 
  
2 DSN Communication Coverage Gap 
 The current NASA Deep Space Network (DSN) 
consists of 13 ground antennas located at three Deep Space 
Communications Complex (DSCC) facilities: Goldstone in 
USA, Canberra in Australia, and Madrid in Spain (Figure 
2). These DSN antennas are required to provide continuous 
communication coverage for deep space flights and 
interplanetary missions. Each DSCC has at least one 34-m 
beam wave guide antenna, one 34-m high efficiency 
antenna, one  70-m antenna, and a signal processing center 
(Figure 2). The three DSCC facilities are not separated by 
exactly 120 degrees, and some DSN antennas are located in 
the bowl-shaped mountainous terrain to shield against 
radiofrequency interference resulting in a coverage gap in 
the southern hemisphere for the current DSN architecture.  
 
 
Figure 2. Overview of antennas and facilities for each Deep Space Communications Complex (DSCC) 
 
 
 
 
Figure 3. 3D profile of DSN communication coverage gap 
 
(a) Altitude of 40,000 km (b) Altitude of 400,000 km 
Azimuth-elevation 
mask for each DSCC – 
from the terrain data 
 
This DSN gap, 
representing the current 
antenna parameters, 
decreases exponentially 
with increase in altitude 
from the Earth’s surface 
 3 
 
The DSN communication gap (Figure 3 and 4) is based on 
the line of sight for each antenna computed using the 
current DSN antenna parameters [3-6], and Azimuth-
Elevation masks that were computed from the terrain data 
for each antenna [1]. As shown in Figure 3, the area of this 
communication gap varies depending on the altitude from 
the Earth’s surface. This communication coverage gap on 
the southern hemisphere is centered at approximate latitude 
of –47° and longitude of –45° (Figure 3 and 4). At an 
altitude of 10,000,000 km, the gap stretches from 
longitudes of –75° to 2° (Figure 4). 
 
 
Figure 4. 2D profile of DSN communication coverage at an altitude of 10,000,000 km 
 
3 PHAs Simulations and Analysis 
The objective of these simulations was to determine 
whether the current DSN antennas are capable of supporting 
a PHA mission. A number of publications have shown the 
need for PHA mitigation planning to protect life on Earth 
from the potential future catastrophic consequences of a 
PHA colliding with Earth. Mitigation planning would first 
require a space mission to carry out fundamental science 
investigations that will lead to designing deflection or 
mitigation schemes. Such missions would study the 
mineralogical and chemical compositions of PHAs, physical 
characteristics, and impact hazards. Whether they will be 
sample return missions or remote sensing science orbital 
payload, navigation and communication back to Earth will 
be required. Authors of [7], [8], and [9] have suggested 
mission lengths ranging from 180 to 365 days. 
 
PHAs were selected for simulations based on the 
following criteria: (i) Earth-close-encounter mission 
opportunity occurring between 2015 and 2040, (ii) Earth 
MOID of less than 0.05 AU, and (iii) the absolute 
magnitude (H) of less than 22. H corresponds to the 
diameter and the albedo of the asteroid 
HD 2.0101329 −=
α
         (1) 
where α  is the geometric albedo of a minor planet or 
asteroid, and D is the diameter in km [8].  
 
Using the above criteria, ephemeris (trajectory) data for 
each PHA selected was obtained by using the HORIZONS 
tool that was provided by the JPL Solar System Dynamics 
Group. These ephemeris data files were used to create 
simulation scenarios for each PHA using Satellite Tool Kit 
(STK) software. In Figures 5 – 11, the ground tracks of 
trajectories of PHAs that fall outside the DSN 
communication coverage gap during close Earth approach 
are highlighted in blue, whereas the PHAs that cross the 
DSN communication coverage gap are shown in red. 
 
3.1 Simulations of 99942 Apophis 
 Figure 5 shows the ground tracks of the trajectories 
for 99942 Apophis (2004 MN4) from April 01, 2028, to 
April 01, 2030. On April 13, 2029, Apophis (about 350 m 
in diameter) will pass 37, 399.5 km (0.10 Lunar distances) 
closer to earth, which is very close to the geostationary 
satellite orbit (~35,786 km). This closer approach will 
provide an opportunity for delivery of a science payload to 
DSN communication 
coverage gap, based 
on the current antenna 
capabilities /  
parameters 
 4 
 
the PHA 99942 Apophis. Several sources have proposed 
99942 Apophis as a good candidate for a test mission. 
During the 2029 closer approach, Apophis will be 
gravitationally perturbed to an orbit that may increase the 
chances of impacting Earth in 2036 [7]. As seen from the 
simulations in Figure 5, 99942 Apophis’ trajectory is within 
DSN communication coverage. 
 
 
 
Figure 5. Simulations of 99942 Apophis 
3.2 Simulations of 1998 OR2 
On April 29, 2020, asteroid 1998 OR2, which has a 
diameter of 3.3 km, will make a close approach to Earth 
within 0.04205 AU (6,298,070 km or 16.4 Lunar distances). 
Figure 6 shows the simulations of the trajectories of 1998 
OR2 from October 29, 2019, to October 29, 2020.  These 
simulations show that 1998 OR2 passes into the DSN 
communication coverage gap during the simulation period. 
However, on April 29, 2020 (close approach date), 1998 
OR2 is above the DSN communication coverage gap, but 
descending down to the gap (Figure 6). The simulations 
show that 1998 OR2 starts crossing the gap at simulation 
time "2 May 2020 00:35:53.818," crosses the gap 8 times, 
and leaves the gap at simulation time "9 May 2020 
01:29:53.818." 
 
 
  
Figure 6. Simulations of 1998 OR2 
 
3.3 Simulations of 2004 QY2 
Asteroid 2004 QY2 will make a close approach of 
0.0471 AU (7,046,060 km or 18.3 Lunar distances) to Earth 
on July 15, 2029. Figure 7 shows the trajectories of 2004 
QY2, starting from January 06, 2029, to December 06, 
2029.  
 
 
           
Figure 7. Simulations of 2004 QY2 
The orbit diagram of 2004 QY2 is shown in Figure 1. From 
the simulations in Figure 7, we can see that 2004 QY2 
3D and 2D ground 
tracks of trajectories of 
Apophis as the Earth 
rotates from April 01, 
2028, to April 01, 
2030.  
Orbit diagram of 
99942 Apophis 
(credit: JPL). 
 (credit: JPL) 
2004 QY2 at simulation time:  
13 Jul 2029 12:56:53.816 UTCG 
DSN coverage 
gap 
DSN 
gap 
From 06 Jan 2029 to 06 Dec 2029 
From 13 Jul 2029 to 17 Jul 2029 
1998 OR2 at simulation time: 
29 Apr 2020 22:32:53.818 
 
1998 OR2 at simulation time: 
9 May 2020 01:29:53.818 
1998 OR2 at simulation time: 
2 May 2020 00:35:53.818 
2004 QY2 at simulation 
 time: 15 Jul 2029 
18:05:10.316 UTCG 
 5 
 
passes into the DSN communication coverage gap about 
two days before its close encounter (on July 15, 2029). 
 
3.4 Simulations of 2001 WN5 
2001 WN5, an Apollo PHA will pass within 254,316 
km (~ 0.6 Lunar distances) from the Earth on June 26, 
2028. 2001 WN5 is estimated to be 700 to 1500 m in 
diameter (http://neo.jpl.nasa.gov).  
 
Figure 8. Simulations of 2001 WN5 
Figure 8 shows the simulations of the trajectories of 
2001 WN5 from January 01, 2028 to December 01, 2028. 
Simulations show that on June 25, 2028, 2001 WN5 crosses 
into the DSN communications gap and stays in the gap for 
about 1.5 hours. 
3.5 Simulations of 2004 BL86 
The PHA named 2004 BL86, which has an estimated 
diameter of 0.5 to 1.1 km, will make the next close 
approach to Earth of 0.008 AU  (1,196,783 km or 3.1 
Lunar distances). Figure 9 shows the simulations of the 
trajectories of 2004 BL86 from June 24, 2014, to June 24, 
2015. During its close encounter (January 26, 2015), 2004 
BL86 orbit falls within the region without DSN 
communication coverage. 
 
Figure 9. Simulations of 2004 BL86 
3.6 Simulations of 2006 SU49 
On January 28, 2029, asteroid 2006 SU49, which has a 
diameter of 0.38 km, will make a close approach to Earth 
within 0.0082 AU (1,226,703  km or 3.2 Lunar distances). 
Figure 10 shows the simulations of the trajectories of PHA 
2006 SU49 from June 01, 2028, to June 01, 2029. From the 
simulations in Figure 10, 2006 SU49 passes into the DSN 
communication coverage gap during its close encounter (on 
January 28, 2029).  
 
 
Figure 10. Simulations of 2006 SU49 
3.7 Simulations of 2010 DM56 
On September 12, 2030, the PHA 2010 DM56, which 
is about 360 m in diameter, will make a close approach to 
Earth within 0.0097 AU (1,451,099 km or 3.8 Lunar 
distances). Figure 11 shows the simulations of the 
trajectories of PHA 2010 DM56 from March 01, 2030, to 
March 01, 2031.  As seen in Figure 11, on September 09, 
2030, 2010 DM56 crosses the region without DSN 
communication coverage. 
 
 
Figure 11. Simulations of 2010 DM56 
4 Summary and Conclusions 
 This study evaluated the current DSN communication 
coverage to support space missions to PHAs. As of 
December 2011, there were 1274 known PHAs 
(http://neo.jpl.nasa.gov/neo/groups.html). The selection of 
PHAs for this simulation was based on Earth-close-
encounter occurring between 2015 and 2040, MOID of less 
than 0.05 AU, and the absolute magnitude (H) of less than 
22.  
  
 The PHA ephemeris data was obtained by using the 
HORIZONS tool that was provided by the JPL Solar 
System Dynamics Group. Then, using PHA ephemeris, 
scenarios for each PHA selected were created and simulated 
using STK software. Table 1 gives a summary of all the 13 
PHAs that were simulated in this study. 
  
2001 WN5 at simulation time:  
25 Jun 2028 01:29:03.816 UTCG 
2004 BL86 at simulation time:  
26 Jan 2015 02:34:13.816 UTCG 
2006 SU49 at simulation time:  
28 Jan 2029 18:18:33.815 UTCG 
2006 SU49 at simulation time:  
1 Feb 2029 12:26:41.130 UTCG 
2010 DM56 at simulation time:  
9 Sep 2030 09:09:53.815 UTCG 
 6 
 
Table 1. Summary of Selected PHAs Simulations 
 
 
 As seen from Table 1, 7 out of 13 PHAs simulated 
cross the DSN communication coverage gap within the 
period of their close encounters with Earth. PHA mitigation 
planning to protect life on Earth from the potential future 
catastrophic consequences of a PHA colliding with Earth is 
a very necessary task. Mitigation planning would require a 
space mission to carry out fundamental science 
investigations that will lead to designing a deflection or 
mitigation scheme.   
 The OSIRIS-REx (Origins, Spectral Interpretation, 
Resource Identification, Security-Regolith Explorer) 
mission is under development and targeted for launch in 
2016 [10]. The OSIRIS-REx mission will intercept asteroid 
1999 RQ36, study the asteroid, return samples to provide 
more knowledge about the solar system, and provide 
knowledge that may guide in deflecting future asteroids 
[10].  1999 RQ36 was not included in this assessment since 
its next close Earth-close-encounter within 0.05 AU will be 
on September 30, 2054 (0.039 AU). 
 For any PHA mission (observation, sample return, 
detonations, deflection, or manned), efficient 
communication to Earth is very critical and essential for a 
successful mission. The maximum period without 
communication coverage if a mission crosses the DSN gap 
is formulated in [1] as 5.12 hours. For the 7 PHAs that 
cross the communication coverage gap, communication to 
Earth can be limited to as little as 19 hours in a 24-hour 
period. This would be unacceptable for a crewed mission. 
Therefore, additional communication infrastructure would 
be required to provide 24-hour coverage for PHA missions. 
Acknowledgment 
 Authors would like to thank Jet Propulsion Laboratory 
(JPL) Solar System Dynamics Group for providing the 
computational program called HORIZONS that was used to 
generate ephemeris data files for PHAs. The authors would 
also like to thank Jon Giorgini from JPL for his generosity 
and help in various aspects during this analysis. 
References 
[1] O. Kegege, et al., “Three-Dimensional Analysis of 
Deep Space Network Antenna Coverage,” accepted 
for publication, IEEE Aerospace Conference, March 
2012. 
[2] JPL, “Near Earth Object Program,” may be found at 
http://neo.jpl.nasa.gov   
[3] JPL/NASA, “Deep Space Network Services Catalog,” 
DSN No. 820-100, Rev. E, December 17, 2009. 
[4] JPL/NASA, “34-m BWG Antennas Telecommuni-
cations Interfaces,” DSN No. 104, Rev. F, June 1, 
2010. 
[5] JPL/NASA, “34-m HEF Subnet Telecommunications 
Interfaces,” DSN No. 103, Rev. B, September 19, 
2008. 
[6] JPL/NASA, “70-m Subnet Telecommunications 
Interfaces,” DSN No. 101, Rev. D, April 21, 2011. 
[7] S. Wagner, et al., “Preliminary design of a crewed 
mission to asteroid Apophis in 2029-2036,” 
AIAA/AAS Astrodynamics Specialist Conference, Vol. 
AIAA-2010-8374, Aug. 2010. 
[8] T. R. Meyer, et al., “Near-Earth asteroid rendezvous 
missions with the Orion crew exploration vehicle,” 
38th Lunar and Planetary Science Conference, No. 
1338, p. 2083, March 2007. 
[9] S. Wagner, et al., “A crewed 180-day mission to 
asteroid Apophis in 2028-2029,” 60th International 
Astronautical Congress, Vol. IAC-09-D2.8.7, Oct. 
2009. 
[10] NASA, “NASA To Launch New Science Mission To 
Asteroid In 2016,” may be found at  
http://www.nasa.gov/home/hqnews/2011/may/HQ_11
-163_New_Frontier.html  
PHA 
Name 
Close Approach  
Date yyyy-
mmm-dd 
Miss 
Distance 
(AU) 
V 
(km/s) 
H 
(mag) 
 
W
ith
 1
00
%
 D
SN
 
Co
ve
ra
ge
 
99942 
Apophis 2029-Apr-13 0.00025 7.4 19.7 Y 
1998 OR2 2020-Apr-29 0.0421 8.7 15.8 N 
1990 MU 2027-Jun-06 0.0308 23.8 14.1 Y 
2004 QY2 2029-Jul-15 0.0471 23.3 14.7 N 
2004 LJ1 2038-Nov-16 0.0198 17.2 15.4 Y 
2004 BL86 2015-Jan-26 0.0080 15.7 18.8 N 
1999 AN10 2027-Aug-07 0.0026 26.3 17.8 Y 
2001 WN5 2028-Jun-26 0.0017 10.2 18.2 N 
1997 XF11 2028-Oct-26 0.0062 13.9 16.9 Y 
2006 SU49 2029-Jan-28 0.0082 4.9 19.5 N 
2010 DM56 2030-Sep-12 0.0097 15.2 19.5 N 
2002 NY40 2038-Feb-11 0.0073 20.6 19.2 N 
2003 AF23 2021-Jan-03 0.0359 15.4 20.6 Y 


Assessment of DSN Communication Coverage for Space Missions to Potentially Hazardous Asteroids

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