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Quick Technical Facts
Technology Milestones
| The eight milestones set forth by NASA for SIM PlanetQuest were as follows: |
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| 1. |
Demonstrate that the brassboard metrology beam launcher is capable of performance that meets both narrow angle and global astrometry requirements.
In other words: Create a high-tech "ruler" for measuring changes in position, with increments of a fraction of the width of a hydrogen atom. |
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Status: Complete. |
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| 2. |
Demonstrate the ability of SIM to stabilize fringes of faint science stars on the science interferometer of System Testbed-3 (STB-3).
This shows that SIM can provide the nanometer control required to enable the Broad Survey and Deep Search for planets, and the Astrometric Grid, and concludes the nanometer control technology phase of the milestones |
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In other words: Create high-tech "shock absorbers" that suppress the effect of tiny vibrations from the machinery, which otherwise would prevent SIM from taking accurate measurements. This solution: SIM compensates for each vibration with an equal counter-vibration. The vibrations being suppressed are extremely small, about 1/50,000th the width of a human hair. |
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Status: Complete. |
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| 3. |
Demonstrate on the Microarcsecond Metrology (MAM-1) Testbed that "angles" (that is, fringe phase delays) between pseudo star sources can be measured at a level consistent with the narrow angle astrometry requirement.
This demonstrates, at the level of a complete stellar interferometer, SIM's ability to meet its requirements for planet finding.
In other words: This puts together all the technology pieces from Milestones 1 and 2 in order to take actual narrow-angle measurements, proving that SIM can detect the tiny "wobbles" of stars induced by the orbits of terrestrial-size planets. |
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Status: Complete. |
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| 4. |
Demonstrate that multiple laser metrology gauges can be integrated into an optical truss representative of SIM's external metrology system. Performance must be sufficient to demonstrate the ability to meet the scientific mission goals for the Broad Survey and the Astrometric Grid.
In other words: Show that several high-tech "rulers," like the one invented in Milestone 1, can work together as a network (that happens to look like a kite) and produce consistent results.
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 The Kite Testbed was developed to test the feasibility of picometer external metrology for SIM. |
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Status: Complete. |
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| 5. |
Demonstrate Microarcsecond Metrology (MAM) Testbed performance of 3,200 picometers over its wide-angle field of regard, consistent with the portion of the SIM astrometric error budget covered by the MAM Testbed.
In other words: This level of performance meets the global astrometry Level 1 requirements of 30 microarcseconds and demonstrates, at the inteferometer sensor level, SIM's ability to determine the astrometric grid. It also demonstrates SIM's ability to meet the global astrometry minimum science requirement. |
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Status: Complete. |
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| 6. |
Benchmark performance of the Microarcsecond Metrology (MAM) Testbed against the narrow-angle goal of 1 microarcsecond. MAM makes measurements of the angular position of a laboratory "pseudostar" as the star is moved over a field of regard just like SIM's (narrow-angle field of 1degree diameter, wide-angle 15 degrees). Technology Milestone 6 is of particular importance since it is the first one to compare current capability against the science goals, rather than the baseline requirements.
In other words: This takes the "baseline" measuring capability demonstrated in Milestone 3 a step further to meet the full science goals in the narrow-angle mode. Narrow-angle measurements are the type SIM will use to detect terrestrial planets. |
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Status: Complete. |
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| 7. |
Benchmark performance of the Microarcsecond Metrology (MAM) Testbed against the wide-angle goal of 4 microarcseconds.
In other words: As with Milestone 6, this takes the measuring "baseline" capability demonstrated in Milestone 3 a step further to meet the full science goals, in this case in the wide-angle mode. SIM will use its wide-angle capability to measure the absolute positions of stars. |
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Status: Complete. |
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| 8. |
The last technology milestone entails building a composite picture of SIM instrument performance from all the technology activities (both testbeds and analysis). This represents the final statement of what level of scientific precision the technology that we have been building for the past decade will be able to provide when it is built into SIM.
In other words: When the various elements are put together (angle measurements, metrology measurements, vibrations and thermal disturbances), all the pieces mesh properly and the instrument works. |
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Status: Complete. |
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