The AIRS and AMSU-A instruments mostly operate autonomously, collecting and sending science and engineering data to the Aqua instrument without intervention from the ground. All channels are used at all times, and the instruments remain on at all times.

Latest Instrument Status

Following are several status reports available:

AIRS operations group

The AIRS instrument suite operations group resides at JPL and is responsible for commanding the instruments, monitoring instrument health, and responding to instrument anomalies. Because of the autonomous operation of the instruments, the operations group normally has little need to actively intervene in instrument operation. Occasionally, the operations group does interrupt the usual operating mode of these instruments. For instance, the operations group intervenes when an anomaly – an unexpected interruption in normal operation, often attributed to a radiation hit that affects instrument electronics – occurs. AIRS has two other categories of operations, both of which are considered routine and not anomalous: calibration and spacecraft maneuvers. (There are no routine AMSU-A operations; that instrument is only commanded in cases of anomaly.)

Calibration tests

The AIRS operations group defines a set of on-orbit calibration tests to determine AIRS performance using the internal calibrators and views to space. These special tests are structured to provide the best spatial, radiometric, and spectral information possible using internal calibration sources and instrument telemetry. Results from the special tests are used to provide a better understanding of the calibration of the AIRS instrument and update calibration coefficients and properties such as detector noise and operability. When a special test is being performed, the data are flagged to process only to Level 1A. This means there will be a gap in the Level 1B, Level 2 and Level 3 data sets during these special tests. The duration of the gap can range from a few granules, for test performed monthly, to up to two days for tests performed rarely.

Reference: Thomas S. Pagano, Hartmut H. Aumann, Steven E. Broberg, Steven L. Gaiser, Denise E. Hagan, Thomas J. Hearty, Mark D. Hofstadter, Kenneth Overoye, Margaret H. Weiler, "On-board calibration techniques and test results for the Atmospheric Infrared Sounder (AIRS)," Proc. SPIE 4814, Earth Observing Systems VII, (24 September 2002);

List of calibration tests performed and corresponding outages

For more information, please see the Instrument Calibration page.

Specific Tests

AIRS-C2, Guard Test: The guard test is run monthly to evaluate the response of the IR detectors under controlled conditions: first, only the “A-side” detectors for each dual-redundant channel are turned on, then only the B-side detectors. This gives the calibration team the information needed to give optimal weights to the A- and B-side for each channel.

AIRS-C5, OBC Cool: The OBC Cool, or OBC Float Test, measures instrument non-linearity with temperature by turning off the on-board calibrator (OBC) and taking data during cool down.

Reference: Thomas S. Pagano, Evan M. Manning, Steven E. Broberg, Hartmut H. Aumann, "Checking AIRS nonlinearity in flight," Proc. SPIE 11127, Earth Observing Systems XXIV, 1112717 (9 September 2019);

AIRS-C7, Space View Noise: The IR detectors are exposed to space or to the onboard blackbody by stopping the scan mirror.

AIRS-C8, Radiation Circumvention: This test is the same as AIRS-C7 above, but also tests the effectiveness of the radiation circumvention circuitry.

AIRS-C9, Scan Profile: The AIRS nominal scan profile is shifted to allow the slow part of the scan to view either the space view or the combined onboard blackbody/Parylene view. This allows characterization of any stray light sources.

AIRS-C10, Lamp Operations: The photometric calibration test, run monthly, turns on each of the three calibration lamps in succession to measure the response of the Visual/Near Infrared (VIS/NIR) detectors.

Reference: Steven E. Broberg, Hartmut Aumann, Evan Manning, Thomas S. Pagano, "AIRS visible light channels: calibration using deep convective clouds," Proc. SPIE 12685, Earth Observing Systems XXVIII, 126850M (6 October 2023);

End of Aqua Prime Mission – Free Drift Constellation Exit and Perigee Lowering Maneuvers

The Aqua spacecraft uses propellant to maintain orbital inclination within the “A-Train” constellation of satellites. The orbit is a sun-synchronous, nearly polar orbit with a mean local time (MLT) at each ascending node (northward equator crossing) of 1:35 p.m. The last set of Inclination Adjust Maneuvers (IAMs) took place in the Spring of 2021. Since then, Aqua has not had enough fuel to maintain its previous inclination and its orbit has been drifting away from the A-Train constellation. Without further IAMs, the MLT drifts in such a way that the ascending node occurs later and later in the afternoon. As shown in the plot below, by January 2025 the MLT will be about 2:30 p.m.

Chart titled "Aqua: Mean local time at ascending node" with mean local time on the y axis and Date on the x axis
Inclination Adjust Maneuvers (IAMs) make it possible for Aqua to maintain a sun-synchronous orbit with a tightly controlled Mean Local Time (MLT) at its ascending node of about 1:35:45 p.m. After late 2021, fuel depletion on Aqua made it impossible to perform IAMs and the MLT has been drifting as shown in this plot. This drift will also result in Aqua’s solar panels generating less power due to increasingly unfavorable angles of solar incidence. The CEMs referred to in the explanation are Constellation Exit Maneuvers, which were not performed in favor of a “free drift” constellation exit. Source: Aqua Flight Dynamics Team.

Aqua plans to execute a series of Perigee Lowering Maneuvers (PLMs) in 2024 to ensure that Aqua meets the requirement to fall out of orbit within 25 years of the end of the science mission. Aqua’s orbital drift will cause decreased solar panel power generation until by mid-2026 there will not be enough power for the spacecraft and its instruments.