attachment_1-technical_appendix__revA.pdf

REQUEST FOR INFORMATION: LARGE DEPLOYABLE ANTENNA FOR

OUTER PLANET MISSIONS – ATTACHMENT 1 - TECHNICAL APPENDIX

Summary The Jet Propulsion Laboratory requests information to support an order of magnitude improvement in data delivery capability from the outer solar system via a large (>6-m) higher frequency (Ka band, ~32 GHz) Reflector-

Boom assembly (RBA). Specifically JPL wishes to enable a >2 Mbps data rate from Jupiter and a >190 Kbps data rate from Neptune. (Data rates assuming >60 dBi Ka gain, 100W amplifier, to single or multiple 34m ground antenna.)

This RFI seeks a feasibility assessment for extending current deployable large aperture RBA technology to outer planets. JPL is requesting this information to inform planning for a set of study contracts under consideration for early 2018. The output of each study contract would allow inclusion of one or more large aperture architectures within an upcoming set of Team X concurrent engineering mission concept studies in preparation for the upcoming

Planetary Decadal Survey.

Background The outer solar system offers numerous cross-cutting opportunities. The planets and moons in the outer solar system provide crucial information about the formation and evolution of the solar system, potential habitats for life, and serve as “ground truth” for the study of extrasolar planets. The Roadmaps to Ocean Worlds report considers five icy moons to have sub-surface oceans and identifies multiple other icy moons that may host subsurface oceans. The giant planets likely encode essential elements of the formation of the solar system, potentially including their migration from where they formed in the proto-solar nebula, and as analogs for extrasolar planets. However, with all of the systems having been explored at least with a fly-by, the need for ever richer data sets and deeper exploration of them is required.

Historically, the data rate from deep space missions has increased by approximately one order of magnitude every decade. Projections for the next few decades suggest a similar increase in demand (Deutsch et al. 2016), driven by a variety of both science and exploration requirements. In the outer solar system, there are multiple drivers for increased data rates and delivered data volumes:

Exploration of ocean worlds, and the desire for a range of more sophisticated in situ sampling as described in the (draft) Roadmaps to Ocean Worlds (e.g., mass spectrometers, gas chromatographs, seismometers);

The Ice Giant Mission concept study identified a broad range of science instruments, including Doppler imaging and a relay capability for an atmospheric probe;

A future Kuiper Belt or “interstellar” mission, such as described by the recent Keck Institute for Space

Studies report, which identified multiple science studies with requirements well beyond those of the

Voyager spacecraft telecommunications sub-system.

To meet these needs an order of magnitude increase in data rate is required. One solution is to use a larger diameter antenna with a higher frequency transmitter than previous outer planet missions.

To assess the ability for current RBA technology to be extended beyond an Earth GEO environment to the outer planets, two sample missions were selected which bound the expected environments: Jupiter and Neptune.

Concept of Operation

Launch

Launch would be on an Atlas V or Delta IV Heavy.

Transit

Transit path varies by mission as shown in Figure 1. For the Jupiter option, the orbit uses a pair of Venus flybys.

For Neptune, an earth flyby is used (not shown in Figure 1) and the spacecraft has a Jupiter flyby on its way out.

Deployment of the antenna would be in one of three options: Soon after launch at Earth orbit, In earth orbit after

Venus flyby or at the target planet after orbit insertion. If deployed an antenna calibration phase would occur prior to orbit insertion. Details are shown in Tables 1 and 2.

Orbit

At the target planet, each mission enters orbit via an insertion burn. The orbits are 60 and 50 days in length, respectively. During a portion of the orbit the spacecraft will turn, settle for a period and then point at earth to download data for a few days. It will then turn back into science mode and collect and store the data for the next pass.

Figure 1. Concept of Operations for Jupiter and Neptune Missions

Table 1 Jupiter and Neptune Mission ConOps Timelines.

Key and Driving Requirements For the purposes of the response, a set of key and driving requirements were determined. This is not a complete set but meant to provide information to inform the response to the RFI.

Functional Requirements

Note that all operational requirements apply only at the target body.

Pointing

The RBA shall point with an electrical boresight error of less than 0.1 deg to the nominal prior to calibration on orbit.

The RBA electrical boresight shall drift less than 0.015 deg from its calibrated pointing during operations.

The RBA electrical boresight shall jitter less than 0.005 deg with a goal of less than 0.001 deg during operations.

Electromagnetic

The RBA shall have an effective 6-m or larger effective RF aperture. Larger apertures are preferred within the stowed volume requirements.

The RBA shall operate in Ka-Band, 32-34 GHz.

The RBA shall be high-gain, >60dBi

The RBA shall have an approximate F/D of 0.65.

The RBA surface RMS nominal is better than 0.4 mm, goal of better than 0.2mm.

The RBA mesh shall be at least 40 OPI.

Mechanical

The RBA shall stow to less than 1.0 m diameter (goal), compatible with the volume available in the stowed configuration figure.

When deployed and the boom fixed to a rigid base, the RBA first mode shall be greater than 1 Hz (goal).

When stowed, the RBA system shall have first modes above 35Hz (compatible with Delta IV launch)

Configuration

The RBA will be stowed within a fairing along the outside of a bus, within a volume allocation as shown in Figure 2.

Responses should consider a deployed RBA as presented in Figure 3, though this suggested configuration can be replaced with a system concept that meets the key requirements.

Figure 2: Stowed configuration cartoon. Notional geometry for reflector and boom volume, dimensions in [mm].

Figure 3: Conceptual cartoon of deployed reflector and boom assembly. 6m reflector shown with F/D=0.65 and feed on the body of the spacecraft.

Environment

Thermal

Radiation

The RBA will be compatible with the worst-case radiation environment for either mission concept: 1MeV electron flux, 10 MeV proton flux.

Mechanical

For launch loadings, assume the environments for a Delta IV heavy.

Response Guidelines The response to this RFI will be in the form of a PDF document and follow the response instructions in the cover letter.

The response should provide discussion of the candidate RBA technology assessing its application to outer planet missions. Special attention is desired in the following areas:

1. Description of RBA Technology

The response should describe the candidate RBA technology. A brief description along with a discussion of its technology readiness and (if applicable) flight heritage. In addition, a discussion of the needs to extend the heritage technology to a 6-m or larger Ka-band reflector with suitable surface accuracy. Architectures that extend to larger apertures are preferred.

2. Survivability

Given the thermal and radiation environments outlined above, can the current materials survive and function both en-route and on-orbit at the outer planets. Provide explanation, including how extensive of a material verification effort would be needed.

3. Deployment

Assess the deployment of the RBA at points 1 (earth at launch), 2 (earth after Venus flyby) or 3 (on-orbit after orbit insertion burn). If deployed at points 1 or 2, given the orbit insertion burns, can the candidate RBA survive while deployed? Would special pointing be needed to protect the stowed or deployed RBA during transit at the higher thermal environment near Venus? Would there be any unique mission operations associated with deployment required? Provide a table of deployment characteristics for each deployment profile.

4. Pointing

Compare the heritage RBA performance with the pointing needed for the outer planet missions. What additional development (if any) would be needed to achieve the desired performance? Provide a pointing table with allocations for each component, with explanation.

5. Verification

Can Heritage RBA test approaches be extended to verify its ability to achieve the surface accuracy in the operational thermal environment? Can Heritage RBA test approaches be extended to verify its ability to achieve the pointing requirements in the operational thermal environment? Provide explanation and a description of the proposed approach for verification of the RBA system.

6. Resources

What mass and volume would you anticipate the RBA requiring? Any unique thermal, power or other resource allocations that would be needed? Provide a breakdown of mass and c.g. estimates for 1) Deployed Reflector, 2)

Deployed Boom, 3) Residual Launch Restraint Hardware. Provide a stowed volume estimate for each component.

Provide a power estimate for the mechanical system during deployment, cruise, and operation. Provide thermal resources required for this system during deployment, cruise, and operation. Provide any other resource requirements that would be discriminators for the proposed RBA concept. Provide explanation for the resource estimates.

7. Other

What additional unique challenges do you foresee in adopting heritage RBA technology to this mission?

8. Study Contract

If a small study contract were established, what tasks would you recommend it focus on?

References Deutsch, L., Townes, S., Liebrecht, P., Vrotsos, P., Cornwell, D. 2016, “Deep Space Network: The Next 50 Years,”

The 14th International Conference on Space Operations.

Delta IV Heavy Payload Planner Guide