NASA WFIRST mission has planned to include a coronagraph instrument to find and characterize exoplanets. Masks are needed to suppress the host star light to better than 10<sup>-8</sup> – 10<sup>-9</sup> level contrast over a broad bandwidth to enable the coronagraph mission objectives. Such masks for high contrast coronagraphic imaging require various fabrication technologies to meet a wide range of specifications, including precise shapes, micron scale island features, ultra-low reflectivity regions, uniformity, wave front quality, etc. We present the technologies employed at JPL to produce these pupil plane and image plane coronagraph masks, and lab-scale external occulter masks, highlighting accomplishments from the high contrast imaging testbed (HCIT) at JPL and from the high contrast imaging lab (HCIL) at Princeton University. Inherent systematic and random errors in fabrication and their impact on coronagraph performance are discussed with model predictions and measurements.
Spitzer Space Telescope was launched on 25 August 2003 into an Earth-trailing solar orbit to acquire infrared observations from space. Development of the Mission Operations System (MOS) portion prior to launch was very different from planetary missions from the stand point that the MOS teams and Ground Data System had to be ready to support all aspects of the mission at launch (i.e., no cruise period for finalizing the implementation). For Spitzer, all mission-critical events post launch happen in hours or days rather than months or years, as is traditional with deep space missions.
At the end of 2000 the Project was dealt a major blow when the MOS had an unsuccessful Critical Design Review (CDR). The project made major changes at the beginning of 2001 in an effort to get the MOS (and Project) back on track. The result for the Spitzer Space Telescope was a successful launch of the observatory followed by an extremely successful In Orbit Checkout (IOC) and operations phase. This paper describes how the project was able to recover the MOS to a successful Delta (CDR) by mid 2001, and what changes in philosophies, experiences, and lessons learned followed. It describes how projects must invest early or else invest heavily later in the development phase to achieve a successful operations phase.
Spitzer Space Telescope, the fourth and final of NASA's Great Observatories, and the cornerstone to NASA's Origins
Program, launched on 25 August 2003 into an Earth-trailing solar orbit to acquire infrared observations from space.
Spitzer has an 85cm diameter beryllium telescope, which operates near absolute zero utilizing a liquid helium cryostat
for cooling the telescope. The helium cryostat though designed for a 2.5 year lifetime, through creative usage now has an
expected lifetime of 5.5 years. Spitzer has completed its in-orbit checkout/science verification phases and the first two
years of nominal operations becoming the first mission to execute astronomical observations from a solar orbit. Spitzer
was designed to probe and explore the universe in the infrared utilizing three state of the art detector arrays providing
imaging, photometry, and spectroscopy over the 3-160 micron wavelength range. Spitzer is achieving major advances in
the study of astrophysical phenomena across the expanses of our universe. Many technology areas critical to future
infrared missions have been successfully demonstrated by Spitzer. These demonstrated technologies include lightweight
cryogenic optics, sensitive detector arrays, and a high performance thermal system, combining radiation both passive and
active cryogenic cooling of the telescope in space following its warm launch. This paper provides an overview of the
Spitzer mission, telescope, cryostat, instruments, spacecraft, its orbit, operations and project management approach and
related lessons learned.
Mission Assurance's independent assessments started during the SPITZER development cycle and continued through post-launch operations. During the operations phase, the health and safety of the observatory is of utmost importance. Therefore, Mission Assurance must ensure requirements compliance and focus on the process improvements required across the operational systems, including new/modified products, tools, and procedures. To avoid problem reoccurrences, an interactive model involving three areas was deployed: Team Member Interaction, Root Cause Analysis Practices, and Risk Assessment. In applying this model, a metric-based measurement process was found to have the most significant benefit. Considering a combination of root cause analysis and risk approaches allows project engineers to the ability to prioritize and quantify their corrective actions based on a well-defined set of root cause definitions (i.e., closure criteria for problem reports), success criteria, and risk rating definitions.
The Spitzer Space Telescope is an 85-cm telescope with three cryogenically cooled instruments. Following launch, the observatory was initialized and commissioned for science operations during the in-orbit checkout (IOC) and science verification (SV) phases, carried out over a total of 98.3 days. The execution of the IOC/SV mission plan progressively established Spitzer capabilities taking into consideration thermal, cryogenic, optical, pointing, communications, and operational designs and constraints. The plan was carried out with high efficiency, making effective use of cryogen-limited flight time. One key component to the success of the plan was the pre-launch allocation of schedule reserve in the timeline of IOC/SV activities, and how it was used in flight both to cover activity redesign and growth due to continually improving spacecraft and instrument knowledge, and to recover from anomalies. This paper describes the adaptive system design and evolution, implementation, and lessons learned from IOC/SV operations.
The Spitzer Space Telescope (formally known as SIRTF) was successfully launched on August 25, 2003, and has completed its initial in-orbit checkout and science validation and calibration period. The measured performance of the observatory has met or exceeded all of its high-level requirements, it entered normal operations in January 2004, and is returning high-quality science data. A superfluid-helium cooled 85 cm diameter telescope provides extremely low infrared backgrounds and feeds three science instruments covering wavelengths ranging from 3.6 to 160 microns. The telescope optical quality is excellent, providing diffraction-limited performance down to wavelengths below 6.5 microns. Based on the first helium mass and boil-off rate measurements, a cryogenic lifetime in excess of 5 years is expected. This presentation will provide a summary of the overall performance of the observatory, with an emphasis on those performance parameters that have the greatest impact on its ultimate science return.