Pith. sign in

REVIEW 4 major objections 4 minor 20 references

On the Size of the Mission Suite Enabled by NASA's Deep Space Network

T0 review · 4 major / 4 minor · reviewed 2026-08-07 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗

Pith's one-line read The paper argues that the Deep Space Network could enable 40 to 70 missions with its current weekly antenna-hours, with the upper end conditional on making antennas interchangeable.

desk verdict A useful, honest capacity estimate whose upper bound is an hour-budget ceiling, not a schedule; the arithmetic needs a cleanup before the 50% growth claim is credible. read the letter →

arxiv 2506.13949 v1 pith:7MTOYCNW submitted 2025-06-16 astro-ph.IM astro-ph.EPastro-ph.SRphysics.pop-ph

T. Joseph W. Lazio (Jet Propulsion Laboratory , California Institute of Technology) This is my paper
classification astro-ph.IMastro-ph.EPastro-ph.SRphysics.pop-ph
keywords DeepSpaceNetworkover-subscriptionmissionsuiteantenna-hoursmultiplespacecraftperantennainterchangeabilityMarsrelayresourceoptimization
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper asks how many science missions the Deep Space Network (DSN) could actually support if the only hard limit is the total antenna-hours available in a week. Using recent tracking data and a simple budget of about 1,512 antenna-hours per week for non-Mars missions, it finds the maximum suite is roughly 40 to 70 missions, meaning up to about 50 percent growth over today's approximately 40 missions. The upper end of that range depends on treating all twelve non-Mars antennas as identical and interchangeable, which they are not; the paper therefore identifies receiver and transmitter standardization as the key lever. It also concludes that multiple-spacecraft-per-antenna (MSPA) techniques, so effective at Mars, would not help elsewhere in the Solar System.

What carries the argument

The central object is a weekly antenna-hour budget, $T_{\mathrm{tot}} = N_{\mathrm{ant}} \times 168\eta$, with $N_{\mathrm{ant}} = 12$ non-Mars antennas and $η = 0.75$ availability, giving 1,512 hours per week. Three allocation models convert that budget into mission counts, using the requirement $T_{\mathrm{science}} ≤ T_{\mathrm{tot}}$ where $T_{\mathrm{science}} = N_A T_A + N_H T_H + N_{\mathrm{PS}} T_{\mathrm{PS}}$ (or the priority-weighted version). The argument also depends on the comparison between the DSN antenna power pattern, roughly 0.066 degrees at X band, and the much larger angular spread of spacecraft around the Moon or Sun-Earth Lagrange points, which is why MSPA does not generalize beyond Mars.

What would settle it

Take the actual 2023 DSN schedule and count, for each antenna, which spacecraft could be tracked given that antenna's receiver bands and transmitter power; if the number of non-Mars missions that can be scheduled at their notional hours is well below 72, the 50 percent growth claim fails even as an hour-budget ceiling. More narrowly, comparing the number of 34-meter antennas with Ka-band capability against the number of spacecraft requiring Ka-band would show whether the interchangeability assumption is the binding constraint.

Watch

Extended reading notes

Core claim

The central claim is that the DSN is not at a hard ceiling: with the current antenna-hours, the mission suite could grow from about 40 to between 40 and 70 missions. The number comes from three allocation models—equal time per mission, mission-specific historical averages, and high/intermediate/low usage tiers—all constrained by the requirement that total demanded hours stay within about 1,512 hours per week. The paper's crucial caveat is that the roughly 70-mission scenario assumes all 34-meter antennas are interchangeable; because actual antennas differ in S-, K-, and Ka-band receiver coverage and transmitter power, the schedulable suite is smaller unless the antennas are made more uniform. The finding that MSPA cannot be extended to the Moon or the Sun-Earth Lagrange points follows from the small angular size of a DSN antenna beam compared with the spread of spacecraft orbits at those destinations.

Load-bearing premise

The load-bearing premise is that all twelve non-Mars antennas can be treated as one interchangeable pool with 75 percent availability; in reality the antennas differ in receiver bands and transmitter power, so the schedulable mission count is lower than the hour-budget ceiling unless those differences are engineered away.

Editorial extensions

If this is right

  • If the DSN antennas were made interchangeable, the network could schedule roughly 70 missions without building new antennas.
  • The current suite of about 40 missions is not maximal; growth of about 50 percent is in principle possible within the existing weekly antenna-hour budget.
  • Expanding MSPA use to the Moon or Sun-Earth Lagrange points would not pay off, because spacecraft there are not clustered within a single antenna beam.
  • Moving science downlinks to K- or Ka-band would either reduce per-mission DSN time or quadruple returned data volume, and the cited mission history suggests operators would choose more science data rather than fewer DSN hours.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • A testable extension: run a scheduling simulation that applies the actual receiver-suite inventory to the Scenario 3 allocation, and compare which missions get blocked; the model's prediction is checkable against the 2023 schedule.
  • An implication the author leaves implicit is that oversubscription should be managed as a soft constraint: mission planners could trade small per-mission time reductions for an additional mission instead of treating the current suite as a hard ceiling.
  • Because the paper's 2023 usage counts include missions from international partners, the headroom for purely domestic deep-space missions may be larger than the 50 percent figure suggests; separating partner missions would refine the growth estimate.
  • The same hour-budget method could be applied to the planned lunar and Lagrange-point fleets as a planning tool, with the caveat that Mars-style MSPA efficiency will not transfer there.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

4 major / 4 minor

Summary. The paper addresses the practical question of how many deep-space missions NASA's Deep Space Network (DSN) can enable, using a weekly antenna-hour budget derived from recent operational data. Three scenarios are considered: equal time per mission (Scenario 1), mission-specific times by Science Mission Directorate division (Scenario 2), and a usage-tiered model with high/intermediate/low allocations (Scenario 3). The paper concludes that the DSN could support roughly 40 to 70 missions, about 50% above the current suite of ~40, conditional on the DSN antennas being interchangeable, and further argues that MSPA is not beneficial outside Mars. The analysis is transparent about its assumptions and limitations, but contains several arithmetic and logical errors that affect the credibility of the upper bound.

Significance. If the results held, the paper would provide a useful quantitative upper bound for DSN mission capacity planning and a clear rationale for investing in antenna interchangeability. The use of real per-mission tracking-hour data (Table 1) and the explicit acknowledgement that the 50% growth claim rests on the false interchangeability assumption are commendable strengths. However, the upper-bound estimate is derived from a weekly total-hour constraint only and is not shown to be schedulable; the paper itself notes that azimuth clumping causes over-subscription. The numerical slips in Scenarios 1 and 3 and the inconsistency between the stated ~70 missions and the actual Scenario 3 total (~78 including Mars) further weaken the central claim. The paper is valuable as a transparent, data-based illustration of an hour-budget ceiling, but it does not currently establish the 'maximum number of missions enabled' as claimed.

major comments (4)
  1. [§3.1] The arithmetic in Scenario 1 is incorrect in two places. First, '31 non-Mars missions + 7 Mars missions' is stated as '36 missions,' but 31 + 7 = 38; if the non-Mars count is strictly less than 31, the maximum is 30 + 7 = 37. Second, the paper states that adding a 32nd mission reduces time per mission to 46.5 hr/week, but with the stated total budget of 1512 hr, 32 missions would allow 47.25 hr/week; the 46.5 hr value corresponds to a total of 1488 hr, not the 1512 hr capacity defined in Eq. (1). This undermines the illustrative degradation calculation.
  2. [§3.3] The allocation reported as the maximum in Scenario 3 violates the paper's own ordering constraint. The text states 'Somewhat by definition, Thi > Tmid > Tlo, and Nhi < Nmid < Nlo,' but the proposed maximum uses Nmid = 34 and Nlo = 33, so Nmid < Nlo is false. Moreover, this allocation is not the maximum under the stated budget: with Nhi = 5, the budget 1512 − 325 = 1187 hr can support, for example, Nmid = 33 and Nlo = 39 (total cost 1185 hr), yielding 77 non-Mars missions, or even larger counts by making Nmid smaller and Nlo larger. Without an explicit additional cap on Nlo, the claimed maximum of 72 missions is unsupported.
  3. [Abstract and §6] The stated upper bound of 'approximately 70 missions' is inconsistent with the model's own output. Scenario 3 yields 72 non-Mars missions (Nhi=5, Nmid=34, Nlo=33), and the paper assumes approximately six Mars missions, giving a total of approximately 78 missions, not approximately 70. The range cited in the abstract and conclusions should be corrected to approximately 40 to 80, or the Mars missions should be excluded from the total in a clearly stated way.
  4. [§3 and Eq. (1)] The central claim that the DSN can 'enable' up to ~70 missions is not established because the model only enforces a weekly total-hour budget (Eq. (1)) and does not analyze instantaneous antenna demand. Figure 2 shows that spacecraft can be clumped in azimuth, implying that at some times more than 12 antennas could be demanded simultaneously; no amount of receiver/transmitter interchangeability creates additional apertures. The 2-hr weekly slack in Scenario 3 leaves no room for such scheduling conflicts. The paper should either present a schedulability analysis or explicitly reframe the result as an hour-budget ceiling rather than a maximum number of missions that can actually be enabled.
minor comments (4)
  1. [§1 and Equation (1)] The symbol for operational availability is written as 'h' in the text but appears as 'η' in Eq. (1); please standardize.
  2. [§4.1] The acronym 'NHROs' is used for near-rectilinear halo orbits; the standard acronym is NRHO. Please correct.
  3. [§6] The conclusions section is numbered '6' but the preceding section is '4.3'; there is no Section 5. Renumber the conclusions as Section 5.
  4. [§3.3] The text states that Thi = 65 hr is 'equivalent to a mission making use of one-half of the (effective) number of hours on a DSN antenna in a week,' but one-half of 126 hr (the 75% availability value) is 63 hr. Please clarify the approximation.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the mission-suite ceiling is an openly stated hour-budget calculation from observed per-mission usage, not a fitted conclusion.

full rationale

The paper's derivation chain is self-contained as a resource-budget calculation. Equation (1) defines available weekly antenna-hours from Nant=12 and eta=0.75 (1512 hr), and Equations (2)-(3) sum required weekly hours across mission categories. The per-mission weekly hour values are taken from observed DSN tracking data in Tables 1, 2, and Figure 5, not from the target conclusion. Scenario outputs are obtained by solving the inequality T_science <= T_tot for the number of missions, so the 72-mission result is an arithmetic consequence of the explicitly stated assumptions (Nhi=5, Thi=65, Tmid=30, Tlo=5). The paper candidly states that 'it is likely that there is no single unique answer' and that different parameter choices would give different results, so the scenario is not presented as a uniquely forced prediction. The upper bound is sensitive to the assumed low-usage tier of 5 hr/week, but that is an openly disclosed modeling choice, not a fitted parameter renamed as a prediction. No load-bearing self-citation or uniqueness theorem from the author's prior work is invoked; the cited references are external (Decadal Survey, DSN handbook, mission papers). The skeptical concern that the model ignores instantaneous antenna-demand conflicts is a correctness/robustness critique, not a circularity of the form where an input is defined in terms of the output or a fitted value is relabeled as a prediction. Therefore no significant circularity is present.

Assumptions & free parameters 6 free parameters · 4 assumptions · 0 invented entities

The analysis is an hour-budget identity with three allocation scenarios. It imports several hand-set quantities from DSN experience, including 12 antennas, 75 percent availability, FY23 per-mission averages, and usage-tier hours, plus one explicitly false idealization, antenna interchangeability. No new physical entities are introduced.

free parameters (6)
  • Number of non-Mars DSN antennas N_ant = 12
    Assumed from 14 total antennas minus 2 effective antennas for Mars; sets total weekly hours in eq. (1).
  • Operational availability eta = 0.75 (126 hr/week)
    Set to 75 percent based on recent DSN experience; directly scales total available antenna-hours.
  • Adopted FY23 per-mission hours TA, TH, TPS = 30, 48, 64 hr/week
    Chosen from Table 2 average and median values for Astrophysics, Heliophysics, and non-Mars Planetary Science; drives the Scenario 2 result.
  • Scenario 3 usage-tier hours Thi, Tmid, Tlo = 65, 30, 5 hr/week
    Chosen from Figure 5 observed usage to represent high, intermediate, and low use; the 72 mission ceiling is an arithmetic consequence.
  • Number of high-usage missions Nhi = 5
    Chosen for illustration in Scenario 3; different choices change the maximum mission count.
  • Mars mission count and effective antenna allocation = 6 to 7 missions, 2 to 3 antennas
    Assumed constant based on recent experience; added to non-Mars totals for the 40 to 70 range.
assumptions (4)
  • domain assumption The DSN has 14 antennas, 12 of which can track non-Mars missions, and each is operational 75 percent of the time.
    Used in eq. (1); operational availability and antenna count are based on recent experience, not measured for this study.
  • domain assumption All non-Mars DSN antennas are interchangeable, with no distinction between 34 m and 70 m or among 34 m receiver suites.
    Implicit throughout section 3 and acknowledged as false in section 4.2; the paper notes this is the crucial caveat.
  • domain assumption MSPA is used only for Mars; no other Solar System location has multiple spacecraft within a DSN beam.
    Stated in section 3 assumptions and analyzed in section 4.1; based on angular sizes of the Moon and Lagrange point halo orbits.
  • domain assumption The FY23 sample in Table 2 and Figure 5 is representative of future mission time demands.
    Per-mission hours are treated as stable notional values; the paper acknowledges the sample is limited in section 3.

how reviews work

0 comments
Cite this review

Pith. "Pith review of On the Size of the Mission Suite Enabled by NASA's Deep Space Network." pith.science (2026). https://pith.science/paper/7MTOYCNW

@misc{pith2026250613949,
  author       = {Pith},
  title        = {Pith review of: On the Size of the Mission Suite Enabled by NASA's Deep Space Network},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/7MTOYCNW}},
  note         = {Machine review of arXiv:2506.13949}
}
read the original abstract

The Deep Space Network (DSN) is the primary means of commanding, tracking, and receiving data from all of NASA's deep space missions, as well as a number of deep space missions operated by other international space agencies. The current number of missions enabled by the DSN is approximately 40 missions, but there has been concern about the level of "over-subscription" of the DSN, namely that the number of missions currently using the DSN is larger than can be enabled reasonably. This manuscript assesses the maximum number of missions that could be enabled, based on recent performance and with the constraint that the total number of hours used per week does not exceed the available number of DSN antenna-hours. Three different models are considered, and the maximal number of missions that could be enabled ranges between approximately 40 missions and 70 missions, assuming that there continues to be approximately six Mars missions and that those Mars missions continue to make use of the DSN's multiple spacecraft per antenna (MSPA) capability. Crucially, the conclusion that an approximately 50% growth in the DSN mission suite rests on the assumption that the DSN antennas are "interchangeable," but they are not, with some spacecraft able to use only certain antennas. Efforts to make the DSN antennas more "interchangeable," primarily in their transmitter and receiver suites, would be an effective means of ensuring expanded capability. Additional findings from this work are that, while additional use of the MSPA capability might appear to be a promising means for increasing the mission suite, there appear to be no locations in the Solar System, other than Mars, for which it would be effective.

Discussion (0). Sign in to comment.

Reference graph

Works this paper leans on

20 extracted references · 18 canonical work pages

  1. [1]

    over-subscription

    18th International Conference on Space Operations, Montreal, Canada, 26 - 30 May 2025 SpaceOps-2025, ID # 610 Page 1 of 11 SpaceOps-2025, ID # 610 On the Size of the Mission Suite Enabled by NASA's Deep Space Network T. Joseph W. Lazio* Jet Propulsion Laboratory, California Institute of Technology, United States, Joseph.Lazio@jpl.nasa.gov * Corresponding ...

    work page 2025

  2. [2]

    over-subscribed

    Introduction There is an increasing level of concern about the extent to which NASA’s Deep Space Network (DSN) is “over-subscribed” and unable to meet even the existing needs for NASA's deep space fleet [e.g., Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023–2032, 1]. Figure 1 provides one illustration of how the n...

    work page 2023

  3. [3]

    over-subscribed

    The number of deep space missions being enabled by NASA's Deep Space Network (DSN) has increased over the past decades, leading to concerns that the network is “over-subscribed.” Shown are the number of DSN antennas in service (black squares) and the average number of spacecraft being tracked (blue circles). If the number of spacecraft varied during a yea...

    work page 2000

  4. [4]

    Both panels show the distribution of the various spacecraft in azimuth as seen from the Goldstone Complex during 2024, with each radial bar representing one spacecraft

    The distribution of spacecraft in the sky changes over time, leading to an inevitable over-subscription of DSN antennas during a typical year. Both panels show the distribution of the various spacecraft in azimuth as seen from the Goldstone Complex during 2024, with each radial bar representing one spacecraft. (left) Week 1, an illustration of a week in w...

    work page 2024

  5. [5]

    The Increasing DSN Load Returning to Figure 1, there are three, non-exclusive explanations for the fact that the number of missions has been increasing over time while the number of antennas has remained essentially constant. Decreased Antenna Time per Mission Given that the number of DSN antennas has remained essentially constant, the total number of ant...

    work page 2025

  6. [6]

    Second, over time scales longer than approximately five years, the actual missions enabled by the DSN can change significantly

    Average Weekly Duration for DSN Tracking of Deep Space Missions Mission FY18 FY22 FY23 (hr) Astrophysics Missions Chandra 44.8 41.2 42.0 TESS 13.9 11.2 11.6 Heliophysics Missions Advanced Composition Explorer 37.2 36.1 34.9 Magnetospheric Multiscale (MMS) 84.4 72.7 66.4 STEREO A 63.5 49.2 44.8 Voyager Interstellar Mission 125.1 132.2 147.8 Wind 31.2 32.6 ...

    work page 2018

  7. [7]

    Morishita, et al., BEACON: JWST NIRCam Pure-parallel Imaging Survey

    T. Morishita, et al., BEACON: JWST NIRCam Pure-parallel Imaging Survey. I. Survey Design and Initial Results, Astrophys. J., submitted (2024) arXiv:2412.04211. 18th International Conference on Space Operations, Montreal, Canada, 26 - 30 May 2025 SpaceOps-2025, ID # 610 Page 11 of 11

    arXiv 2024

  8. [8]

    != 𝑁#$!× 168𝜂 hr =1512 hr.%&'%/.)!

    Projections for the Future This section considers what might be the maximum number of missions that could be enabled by the DSN, without significant reductions to the amount of time per mission. I consider three different scenarios, designed to illustrate the potential range of answers. However, it is likely that there is no single unique answer. Beyond t...

    work page 2025

Show all 20 references
  1. [10]

    priority

    3.3 Scenario 3: Usage-Based Mission Scheduling In this scenario, the DSN time allotted to a mission is based in some measure on a “priority.”1 While many ap-proaches could be adopted, I choose a simple one in order to illustrate the potential results. I assume that missions ar...

    2025

  2. [11]

    may result in times such that only low usage missions are able to be tracked at some times of the day. For this scenario, the total number of hours for (non-Mars) science missions is Tscience = NhiThi + NmidTmid + NloTlo, (3) where Nhi, Nmid, and Nlo are the number of high-, i...

    2023

  3. [13]

    at” a Sun-Earth Lagrange point, spacecraft are in “halo

    Additional Topics In this section, I expand upon various topics noted earlier. 4.1 Multiple Spacecraft per Antenna (MSPA) As noted above, the MSPA technique has introduced considerable efficiencies for Mars missions, enabling science data from up to four spacecraft at or on Ma...

    2025

  4. [14]

    National Academies of Sciences, Engineering, and Medicine, Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023–2032, The National Academies Press: Washington, DC, 2022, doi: 10.17226/26522

    2023 doi

  5. [15]

    C. D. Edwards, Jr., C. T. Stelzried, L. J. Deutsch, L. Swanson, NASA's Deep-Space Telecommunications Road Map, Telecommunications and Mission Operations Progress Report 136 (1998)

    1998

  6. [16]

    L. J. Deutsch, S. A. Townes, P. E. Liebrecht, P. A. Vrotsos, D. M. Cornwell, Deep Space Network: The Next 50 Years, SpaceOps 2016 Conference, American Institute of Aeronautics and Astronautics, Reston, VA

    2016

  7. [17]

    D. A. Caldwell, et al., Instrument Performance in Kepler's First Months, Astrophys. J. 713 (2010) L92

    2010

  8. [18]

    Zurek, et al., MRO overview: Sixteen years in Mars orbit, Icarus 419 (2024) 116102

    R. Zurek, et al., MRO overview: Sixteen years in Mars orbit, Icarus 419 (2024) 116102

    2024

  9. [20]

    C. C. Williams, et al., The PANORAMIC Survey: Pure Parallel Wide Area Legacy Imaging with JWST/NIRCam, Astrophys. J. 979 (2025)

    2025

  10. [31]

    Strikingly, if this illustrative upper limit is combined with a characteristic number of Mars missions, the total number is 36 missions (» 31 non-Mars missions + 7 Mars missions), the resulting number is only slightly lower than the DSN's current mission suite (» 40 missions, ...

    2025

  11. [2018]

    The number of missions has grown from 35 in (fiscal year) 2015 to 40 in (fiscal year) 2023, an increase of approximately

    From Table 1, there is no clear evidence that more science missions are being enabled by a trend of reduced time per mission. The number of missions has grown from 35 in (fiscal year) 2015 to 40 in (fiscal year) 2023, an increase of approximately

    2015

  12. [2023]

    18th International Conference on Space Operations, Montreal, Canada, 26 - 30 May 2025 SpaceOps-2025, ID # 610 Page 8 of 11 Figure

    2025

Pith tools

Reviewed August 7, 2026 · model on record in the stance chip above.