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NEOSSat Science Guest Observation (GO) Program Cycle 5

On this page

  1. Scope of Program
  2. The NEOSSat Mission
  3. The Shared Observer Program
  4. References
  5. FAQ (Frequently Asked Questions)
  6. Appendix A.1: Photometry example
  7. Appendix A.2: Astrometry examples
  8. Appendix B: AO request form for observation time.

Announcement of Opportunity (AO)

Cycle 5 period: to

Publication date:

Application deadline:

For a list previously approved observers, see NEOSSat: observing asteroids, space debris and exoplanets | Canadian Space Agency (

1. Scope of Program

In this section

This fifth issue of the NEOSSat opportunity follows the same process as for Cycle 4. Observers from Cycle 4 who wish to continue their observing campaigns must re-apply. All applications will be competed and evaluated according to the criteria in 3.3.4.

1.1 Overview

Figure 1 Depiction of NEOSSat micro-satellite in space. (Credit: CSA)

The Canadian Space Agency (CSA) solicits proposals for the acquisition and analysis of new scientific data from the NEOSSat (Near-Earth Object Surveillance Satellite) space telescope. Unaffected by day/night and weather conditions, NEOSSat is able to perform space-based imaging including conducting photometric studies with precision sufficient to perform asteroseismology studies and other variability analyses of stars and exoplanet systems. NEOSSat has already demonstrated imaging and photometry of certain exoplanet transits (see example in Appendix A1). NEOSSat is well-suited for the study of near-Earth asteroids or comets as it provides near-Sun observing capabilities and can provide direct parallax measurements of nearby objects due to its orbit around Earth. This is demonstrated in examples shown in Appendix A2, and Ref 4.c. Astrometric observations have been submitted to the Minor Planet Center, under NEOSSat's observatory code C53.

The intent of this AO is to offer observation time on NEOSSat to the scientific community on a competitive basis. CSA is not planning to issue grants as part of this announcement of opportunity (AO). Successful applicants will retrieve requested data on the CSA open data portal or from the CADC. There will be no proprietary period applied to the acquired datasets. (Note that all data from previous cycles are available on CADC and CSA Open Data portal.)

1.2 Responding to this AO

Please use the request forms in Appendix B to detail your planned use of this space telescope. The forms or any questions on the AO are to be sent to this email address: New email adress

Please note that Earth observations or imaging of satellites or space debris are not eligible.

2. The NEOSSat Mission

In this section

2.1 Mission overview

The Canadian NEOSSat micro-satellite orbits in a sun-synchronous orbit at 785 km altitude over the terminator of the Earth with a 100 min period (15 orbits per day). NEOSSat, with heritage from the MOST space telescope, features: onboard star catalog enabling rapid all-sky target acquisition; an extended baffle for low solar elongations observations; accurate tracking of moving objects; and a shutter enabling dark images.

NEOSSat has a single visible-band instrument, a 15-cm telescope with two 1024 × 1024 frame-transfer CCD detectors (Figure 2) and no filters. One CCD is dedicated for fine guidance (star tracking), while the other imager is used for the science. The instrument specifications are provided in Table 1.

Table 1 NEOSSat Payload specifications
Telescope 15 cm diameter, F/6 Rumak-Maksutov with field flattening lenses
Imager CCD back illuminated AIMO device E2V 47-20, 1024×1024 pixels
Spectral range 350 – 1050 nm (there is no photometric filter)
System QE peak 0.78 @ 600nm
Science FOV 0.86 x 0.86 deg (subrasters possible to increase cadence, see below)
Pixel size 13 x 13 μm
Pixel scale 3 arcsec/pixel
PSF Approx. 2 pixels FWHM
Limiting magnitude V~19.5 (stacking or 100 sec exposure, after image post-processing)
Baffle 90 cm long, to reduce stray light from both sun and Earthshine.
Target nominal constraints
  • 40 deg. min solar elongation (12 degrees min solar elongation during orbit eclipses)
  • 10 deg. above Earth illuminated limb
  • 10 deg. from Moon
Shutter Between the two field lenses, used for safety and dark image calibration
Pointing knowledge 1.2 arcsec (demonstrated performance)
Stability 0.5 – 1 arcsec for 100 second exposure (after settling)
Tracking Up to 60 arcsec/sec (in RA and Dec)
Min max exposures 0.002 to 100 sec (longer possible)
Raster size Configurable based on need
Imaging cadence as a function of raster size
  • 1024×1024: 50 sec
  • 512×512: 15 sec
  • 256×256: 5 sec
  • (applicants may send a request using the email address in Section 1.2 for other options or get updated cadence performance)
Photometric precision Better than 1 mmag demonstrated, but depends on SNR
Astrometric precision Centroid to sub-pixel, demonstrated by stacking multiple images

Figure 2 NEOSSat optical efficiency. This figure illustrates the relative spectral response of the CCD (quantum efficiency) superimposed on the solar spectrum and net instrument efficiency. (Credit DRDC)

2.2 Operations

NEOSSat operations are conducted by the CSA. The Satellite Operations team schedules observations, directs the satellite, collects the data, and monitors the health of the spacecraft and its payload. Data is downlinked typically four times daily and archived at the CSA headquarters (St-Hubert, QC). Astronomy images (in the FITS format, as detailed in Ref 4.d) are automatically distributed to CSA's Open Data portal, and also to the CADC, as discussed in Section 2.5.

2.3 Orbit and continuous viewing zone

NEOSSat's polar Sun-synchronous orbit over the terminator of the Earth results in a nominal Continuous Viewing Zone (CVZ). The CVZ is illustrated in Figure 3. The telescope can point to a target in the CVZ from any point in the orbit. There are some restrictions on the spacecraft pointing, including roll angle, due to operational constraints and spacecraft thermal constraints, which place some additional limits on CVZ access or continuity.

Figure 3 CVZ in yellow illustrates where the telescope can point at any time in the orbit, function of date. The telescope can point towards the sun respecting a minimum 40 deg. elongation. The scale on the right is the total target time. (Credit Jason Rowe, Bishop's University)

Observation fields outside the CVZ can be observed by NEOSSat, but without continual coverage during a given satellite orbit. It is possible to share each NEOSSat orbit with several target fields depending on the time-sampling requirements set by the science.

The spacecraft faces an annual orbital "eclipse season" during which the satellite is in the Earth's shadow for up to fifteen minutes every orbit. This occurs from late October to late January each year. Note the AO Cycle 5 covers the eclipse period. (The last full eclipse condition will be on .)

Special considerations for observing in eclipse: A 2-minute minimum acquisition time is typically allocated after eclipse begins and the rest of the time should be available for imaging the target. Operationally it is a good strategy to aim the telescope near the target in advance to minimize the acquisition overhead. If slews are timed properly, the satellite can arrive at the target just after it enters eclipse. Normally there is a 2-minute settle time to achieve fine pointing, but can be less if the prior slew is not large. For large slews, we use a slew rate of 1 deg/s.

While NEOSSat can image from anywhere in its orbit, imaging done in the South Atlantic Anomaly (SAA) is subject to CCD noise due to charged particle bombardment (Figure 4). Depending on the scientific objectives, imaging is often avoided while crossing the SAA.

Figure 4 South Atlantic Anomaly (SAA) affects portions of 11 of 14 daily orbits, either on the ascending or descending node. (Credit CSA)

NEOSSat has the capability to track comets and asteroids by performing a fine slew at constant right ascension and declination rates. This is achieved by specifying a starting right ascension and declination and then commanding NEOSSat to fine-slew at the target's angular rate (up to 60 arcsec/sec max). For objects with angular rates lower than 1 arcsec/sec it is recommended to acquire imagery in inertially fixed acquisition mode.

2.4 Instrument focal plane and exposure times

NEOSSat is equipped with two identical CCDs – one dedicated to science imaging and one as a star tracker.

Although the structure and optics were designed to be athermal, some defocus is still apparent over certain temperature ranges. There is no active temperature control system for the instrument. Depending on the scientific goals, satellite pointing strategies may be employed to manage instrument temperatures and optimize focus.

There is a shutter on the CCD camera which can be commanded to generate darks for calibration. Requirements for darks should be provided by the user and may be scheduled during certain satellite operations.

Exposure times are accurately controlled by rapid frame transfer CCD. Achievable imaging cadence depends on the exposure length and number of pixels being transferred, which can be controlled based on user-selected raster size and binning. Simultaneous readout and exposure is also supported when exposure length exceeds the readout/transfer time, which can increase the image cadence.

The spacecraft typically achieves pointing stability of about 1 arcsec RMS, so most of the image wander is around 1/3 pixel in the focal plane. Such pointing stability is achieved after a certain settling time. Imaging done before settling time may demonstrate jitter, but for short exposures this may be inconsequential.

Figure 5 NEOSSat photometric error as a function of magnitude based on a star field near star AU Mic. This figure illustrates that the photometric precision is below 0.02 for stars brighter than magnitude ~14 and the fractional errors increase exponentially for fainter stars. (Credits: Jason Rowe, Bishop's University)

The telescope has a baffle (Figure 1) limiting the amount of stray light due to bright objects such as the Sun, the Earth's limb or the Moon. The roll angle of the spacecraft is selected to block stray light. The telescope baffle was designed to allow pointing at 45 degrees of solar elongation; although imaging at 40 degrees has been demonstrated.

2.5 Data processing and archiving

NEOSSat science data (raw data - level 0) is downloaded, processed, and archived at CSA in FITS format. The raw astronomy images are copied automatically to CSA's Open Data archive, accessible from:

The data is also archived, on a regular basis, at the NRC Canadian Astronomy Data Centre (CADC).

Investigators from selected observer programs are expected to pick up their data from these portals. There is no proprietary period following image reception and the data is visible publically.

In general, NEOSSat observers are responsible for their own data processing, including noise removal and other corrections. Some NEOSSat image processing software is publically available as open source at: GitHub : An exposure time calculator (ETC) is also available. CSA is planning to introduce some of the open source image reduction tools into its automation pipeline in order to make processed data available to all users.

3. The Shared Observer Program

In this section

Given that the spacecraft is time-shared with Defence Research and Development Canada (DRDC), with required spacecraft maintenance,a few hundred hours per year is available for astronomical observations.

3.1 Observing Time Allocation

With the CSA / DRDC joint project, observing time allocation will have to be shared and prioritized. DRDC and astronomical targets of opportunity (ToO) will be considered any time and prioritized. In routine scenarios, it is expected that astronomy tasking will be interspersed with DRDC tasking. Depending on the scientific observation strategy, a few continuous days in a given week could be available for astronomy, if needed.

3.2 General Observing Constraints

For Cycle 5, proposals are expected for observations within the AO period specified, with likelihood of producing some results in that period. New proposals can be submitted in subsequent cycles to follow up on findings/data sets from prior cycles. It is possible that the observation period may continue past the declared end date, until Cycle 6 commences. (See below for targets of opportunity.)

3.3 Proposal Requirements

3.3.1 Who May Propose

The intent of this program is to enhance Canadian scientific development. Therefore, only Principal Investigators (PI) affiliated with Canadian institutions are eligible to propose for NEOSSat guest investigations through CSA. A PI can be a professor, post-doc, graduate student and other researcher. The requirement of affiliation with a Canadian institution does not extend to Co-Investigators (Co-I). A Canadian institution can be a university or post-secondary institution, a government department, ministry, or agency, a federal or provincial research institute or lab. Companies and non-government organizations with research interests are also eligible.

3.3.2 Target Specification

All proposals are required to include a target table to specify desired observing modes and other required parameters as specified in the request form (Appendix B). CSA will review the feasibility of observing the targets considering NEOSSat constraints, such as schedule, limiting magnitudes, duration, availability of star tracking stars in the field.

Targets of Opportunity (ToO).

If a PI expects to observe new targets or events, aka "Targets of Opportunities", during this Cycle, we encourage a proposal, before the application deadline, that describes the anticipated ToO. An "anticipated ToO" proposal must describe the types of targets and observation modes as well as the possible number of occurrences; it must also address the criteria described in Section 3.3.4. If the "anticipated ToO" proposal is accepted, then follow-up arrangements will be made between the PI and the NEOSSat operations team for scheduling specific imaging task requests, when required. A best effort will be made to execute the observations, which may depend on imaging feasibility and schedule conflicts. Scheduling challenges may result from the short delay between the request and the observation, established priorities with other scheduled observations and satellite availability (including considerations that satellite operations occur mostly during regular business hours). Targets of opportunity may also be submitted throughout the cycle, with priority typically given to participating Guest Observers of the active cycle.

3.3.3 Submission of Proposals

Prospective proposers to the NEOSSat GO program must adhere to the following procedures for proposal submission, as indicated in the request forms:

  • A PDF form template must be completed and should include a description of the scientific objectives, a demonstration of the feasibility of the proposed observations, and how the proposal will utilize the unique capabilities of NEOSSat to carry out the investigation. The scientific justification should not exceed 4 pages. Tables and figures are not counted in the page limit.
  • In case a double blind review process is followed, the authors are encouraged to write their proposal (page 2 of the PDF form) such that the identities of the PI and co-I's are not mentioned.
  • An Excel spreadsheet template is provided to specify the requested observations details.
  • Submit the completed proposal forms through the email address in the AO (Section 1.2). Hard-copy submissions are not requested.
  • All electronic proposal materials must be sent by 23:59 (EST) on the due date for this program given on the first page of the AO.

3.3.4 Evaluation and Selection of Proposals

Proposals submitted to CSA in response to this solicitation will be evaluated with respect to these criteria which are intrinsic merit, relevance, and feasibility:

  1. Science merit, justification of the investigation and potential impact to the science field.
  2. The suitability of using the NEOSSat observatory for the proposed investigation;
  3. The degree to which the investigation uses NEOSSat's unique capabilities;
  4. The feasibility of the proposed investigation, considering NEOSSat's observational constraints; and
  5. The commitment of the PI to undertake the analyses and publish results.

A CSA review panel, including possibly expert members from the community, will review proposals according to the above evaluation criteria and decide on time allocations.

3.3.5 Notifications

Email acknowledgements will be sent when applications are received. The PI will be notified regarding the success of their application within 3 weeks after the closing date of the AO. PIs of successful proposals will be provided further information regarding their observation runs and data availability and distribution.

4. References

  1. NEOSSat CSA webpage:
  2. MOST CSA webpage:
  3. Conference Proceedings: Abbasi, V., Thorsteinson, S., Balam, D., Rowe, J., Laurin, D., Scott, L. and Doyon, M., (). The NEOSSat Experience: 5 Years in the Life of Canada's Space Surveillance Telescope - 1st ESA NEO and Debris Detection Conference (). Available here:
  4. NEOSSat FITS User's Guide to FITS V3 available here:
  5. NEOSSat Open Government portal:
  6. CSA's Open Data portal:
  7. NRC Canadian Astronomy Data Centre (CADC)

5. FAQ (Frequently Asked Questions)

Applicants can obtain clarification on the AO, if necessary, before submitting a request for time. For any questions related to the AO, please use the email address in Section 1.2. Questions and answers will be posted on this webpage below. (Questions received might be rephrased and will be posted anonymously.)

6. Appendix A.1: Photometry example

Figure A.1 Photometry of WASP-33 by NEOSSat (blue points); comparison star (pink). Expected, not fitted, signal (red). The photometry is non-differential. (Credit: Jason Rowe, Bishop's University)

7. Appendix A.2: Astrometry examples

Figure A.2. Near-Earth asteroid 2017-VR12 (boxed) seen on UT at a distance of 0.010 AU and projected on ecliptic J2000 coordinate frame. Streaks are geostationary satellites. NEOSSat tracked 2017-VR12 closely at its Earth fly-by. (Credit: David D. Balam, Spaceguard Consulting)

Figure A.3. The effect of parallax upon a stack of 70 images, obtained through 1/3 of the orbital period of NEOSSat. The object is Periodic Comet Wirtanen (46P) as seen on UT when the comet was 0.116 AU from the Earth. The geocentric motion vector was 261 arcseconds per hour at position angle 26.5⁰. (Credit: David D. Balam, Spaceguard Consulting)

8. Appendix B: AO request form for observation time.

Responding to this AO requires completing as much as possible the PDF and Excel forms provided. The completed forms will be shared only with the CSA and the review committee. In the subject line of your email, please indicate "NEOSSat AO Cycle 5" and optionally add your subtopic if pertinent such as the title of your proposal as well as adding the PI name to the filenames submitted.

Please fill out the template Excel spreadsheet with your observation timings. This completed spreadsheet will help to streamline the user requests with the satellite scheduling.

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